Editing UNSC Marine Corps

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{{Ratings}}
{{Infobox Military Unit
|unit_name=UNSC Marine Corps
|image=[[Image:1209088725 Marines.PNG|350px]]
|dates= Since [[2163]]
|country= 
|allegiance= [[United Nations Space Command]]
|branch=[[United Nations Space Command Defense Force]]
|type= 
|role= 
|size=
|command_structure=
|garrison= 
|garrison_label=
|nicknames= "Leathernecks"
|patron=
|motto=
|colors=
|colors_label=
|march=
|mascot=
|anniversaries=
|equipment=
|battles= 
*[[Insurrection]]
**[[Operation: TREBUCHET]]
*[[Human-Covenant War]]
**[[Battle of Harvest]]
**[[Battle of Sigma Octanus IV]]
**[[Battle of Reach]]
**[[Battle of Installation 04]]
**[[First Battle of Earth|First]] and [[Second Battle of Earth]]
**[[Battle of Installation 05]]
**[[Battle of Installation 00]]
|decorations=
|battle_honours=
|commanders=*[[General|Gen.]] [[Kits]]
*[[Major General|MajGen.]] [[Nicolas Strauss|N. Strauss]]
*[[Major|Maj.]] [[Antonio Silva|A. Silva]]
*[[Captain (Marine Corps)|Capt.]] [[Ponder]]
*[[First Lieutenant|1stLt.]] [[Melissa McKay|M. McKay]]
*[[Sergeant Major|SgtMaj.]] [[Avery Johnson|A. Johnson]]
*[[Gunnery Sergeant|GySgt.]] [[Pete Stacker (Marine)|P. Stacker]]
*[[Gunnery Sergeant|GySgt.]] [[Reynolds]]
|notable_commanders=
}}
{{Quote|They're the best of the best, but they're only human.|Halo CE Manual}}

The '''United Nations Space Command Marine Corps''' is a branch of the [[United Nations Space Command|UNSC]] [[United Nations Space Command Defense Force|Defense Force]] that is responsible for land-based military operations as well as the protection of [[UNSC Navy|Naval]] vessels and installations from attack.

A rugged and diverse assortment of well equipped and highly trained men and women, one of the Marine Corps's most notable conflicts was fighting a [[Human-Covenant War|losing war]] against the [[Covenant]]'s highly superior technology and numbers. Under the leadership of many notable commanders such as Captian Jacob Keyes and Sergent-Major Avery Johnson, they continued to wage a furious struggle against the [[Covenant]], even as their numbers diminished.

==History==
===Before The Human-Covenant War===
The [[UN Marine Corps]] (The predecessors of the UNSC Marine Corps) were one of the primary combat groups fielded by the UN in the [[Interplanetary War]], and were the first military organization [[Argyre Planitia Campaign|deployed offworld]] in 2163. After the [[United Nations]] claimed victory in [[2164]], it reorganized into the [[UNSC]], thereby changing the UN Marine Corps to the UNSC Marine Corps. Later, the UNSC Marine Corps would be responsible for dealing with [[Insurrectionist]] uprisings among UNSC colonies star systems.

===First Encounters===
[[Image:Halo Wars Marine BR.jpg|right|thumb|UNSC Marines fight [[Elite]]s with [[BR55HB SR Battle Rifle|Battle Rifles]] in one of the Marine Corps's first battles against the [[Covenant]].]]
[[Image:Screenshot 6 preview.jpg|thumb|Another early encounter against the [[Covenant]].]]
[[Image:Rendermarine.jpg|thumb|A ''[[Halo Wars]]'' Marine firing an [[M90 Shotgun]].]]
[[Image:Harvest_battle.jpg|right|175px|thumb|The Battle of Harvest]]
The first documented Marine Corps encounter with the [[Covenant]] was at the [[First Battle of Harvest]], but there was only a light Marine presence, made up of [[Colonial Militia]] and civilians.

The first major encounter occurred during the [[Second Battle of Harvest]] in the [[Epsilon Indi System]]. The marines quickly established a [[Alpha Base (Harvest)|base of operations]] in Harvest's arctic region, while a reconnaissance team was sent to scout the surrounding area, though they were killed by [[Energy Sword]]-wielding, [[Special Operations Elite]]s, under the command of an [[Unnamed Arbiter|Arbiter]]. In response, a detachment of [[Scorpion]] tanks, and [[Warthog]] light-medium reconnaissance vehicles were sent to investigate, and were met by a Covenant heavy battle-group, with large numbers of [[Banshee]] attack fighters and [[Sanghelli|Elite]] warriors. The [[UNSC]] force suffered heavy casualties. After this encounter, Alpha Base was lost to the Covenant, and [[Sergeant (UNSC)|Sergeant]] [[John Forge]] had to lead an armoured column of [[Warthog]]s to retake the base and remove a Covenant force inside an ancient [[Foreunner]] structure so [[Ellen Anders]] studied it. However, when inside the artifact, the force was pinned down by a group of SpecOps Elites, and [[Grizzly|Grizzlies]] had to be sent down to relieve the Marine force.<ref>''[[Halo Wars]]''</ref>


== [[Arcadia]] ==
The only thing the relic did while the UNSC was there was pointing to Arcadia. Once inside the ship, Anders insisted that what was in Arcadia could be the key to win the war and they had to find it before the [[Covenant]]. Finaly, [[James Gregory Cutter]] accepted and they went to Arcadia. The Covenant where already there, attacking the city. Local forces and the Spartan Red Team asked the [[UNSC Spirit of Fire]] help. The ship send down a group of hornets, commanded by Forge. UNSC forces where trying to evacuate civillians in thre main cargos. Cargo 3 was destroyed, but the other two cargos survived and evacuated. After that, the Covenant raised a huge plasma shield over the planet, the UNSC  needed to look why they made that, so they used a prototype af Plasma Rhynos to destroy the shield. After that, Forge's forces advanced and saw that the Covenant were trying to build a [[Scarab]]. They eventually destroyed it, but when Ellen Anders was studing it, the Arbiter took her to a Forerunner shield world in order to realese a [[Forerunner]] Fleet.


== Shield World ==
The Spirit of Fire followed the Covenant ship to the Shield World. Once there, UNSC forces encountered the Covenant. Eventually, they discovered that the planet was all covered by the [[Flood]] Infection. After some combats, they followed Anders signal and discovered the she and the Covenant where inside the shield planet. The Covenant used Ellen to realese the fleet, but then, Anders scaped and was found by Forge. Ellen Anders warms the UNSC forces what the Covenant were planning to do, and finaly decided to use the Spirit's energy core to make a star inside the plannet turn into supernova and destroying the fleet. When the UNSC forces and the Spartan Red Team where activating it, they were attacked by the Covenant and the Arbiter, who was finaly killed by [[John Forge]]. Unluckily, the core was damaged, making somewone necessary to activate it manualy, and die. Forge decides to stay in the core, and then finaly the UNSC evacuates all forces. The mission is a succes, destroying all the Forerunner Fleet. 

===[[Battle of Sigma Octanus IV]]===
There was a Marine presence on the colony world of [[Sigma Octanus IV]]. In the first stage of the battle, during a naval engagement, a [[Covenant Carrier]] was able to land a large contingent of troops on the northern pole of the planet. 

The Covenant were able to take [[Côte d'Azur]], a major population center. Fortunately, almost all of the civilian population was able to be evacuated beforehand, and [[UNSC]] Marine Corps [[General]] [[Kits]] launched an assault by 0700 hours to retake the city. It was unsuccessful.

Meanwhile, three Marine squads, near Côte d'Azur and under the command of [[Lieutenant]] [[McCasky]] were dispatched for a light reconnaissance of [[Sigma Octanus IV Grid 13 x 24|Grid 13 x 24]]. They were engaged by [[Covenant]] forces, including [[Mgalekgolo|Hunter]]s, and suffering heavy losses, only one UNSC [[Warthog|M12 Warthog LRV]] of the reconnaissance force survived with four Marines by the names of [[Harland]], [[Walker]], [[Fincher]], and [[Cochran]]. Shortly afterwards, [[Firebase Bravo]] was destroyed by the Covenant, and the [[Warthog]] was forced to divert to [[Alpha Headquarters]].  

It, too, had been attacked, and while the Covenant attack had been repulsed, heavy casualties were suffered which left Harland the temporary commander of the base. Harland promptly requested reinforcements from the cruiser in orbit, the [[Leviathan]].  The ''Leviathan'' sent a team of twelve [[SPARTAN-II]]s commanded by [[SPARTAN-117]] as reinforcements.<ref>''[[Halo: The Fall of Reach]]'', page 174</ref>.

The surviving Marines of Marine HQ protected a [[Pelican Dropship]] while the SPARTANs detonated a [[HAVOK Nuclear Warhead]] in Côte d'Azur, cleaning the Covenant ground presence on Sigma Octanus IV. They then retreated back to a Pelican dropship, which promptly took off with other Pelicans holding other Marine survivors for the UNSC ''Leviathan''<ref>''[[Halo: The Fall of Reach]]'', page 212</ref>.

===[[Battle of Reach]]===
The UNSC Marine Corps maintained a sizable presence of [[Reach]] when the Covenant stormed the planet, bypassing the defense fleet in orbit and the [[MAC Gun]] platforms thus make a landing of large numbers of soldiers on the South and North poles. 

By 0555 hours, the Covenant had overrun [[FLEETCOM HQ]] on Reach, destroying the perimeter and swarming the Marine defenders with [[Banshee]]s, [[Type-25 Assault Gun Carriage|Wraith]]s, and battalions of infantry. The objective of the Covenant ground armies was to destroy a series of fusion reactors on Reach's surface that powered the orbiting [[Super Magnetic Accelerator Cannon]]-equipped [[Orbital Defense Platform]]s, and thus, disabling the UNSC's major defensive asset and allowing the Covenant fleet to occupy Reach's airspace.

By 0622 hours, the situation was critical enough that the {{UNSCShip|Pillar of Autumn}} sent a full detachment of [[SPARTAN-II]] super soldiers to Reach in a [[Pelican]] drop ship to defend the fusion generators. The [[Orbital Defense Platform]]s were already being vaporized in space, and if they were compromised from the ground, the meager remaining UNSC defense fleet would swiftly fall. 

Meanwhile, [[Charlie Company]], a Marine detachment, was in charge of defending [[Orbital Defense Generator Facility A-331]]. They were forced to defend against a massive Covenant attack, using chain guns on Warthogs, Tanks,and positions from the bunkers, as well as any arsenal available.  [[Lieutenant]] [[Buckman]], the CO of Charlie Company, was ordered to flank the Covenant to retrieve the [[NOVA]] bombs, but FLEETCOM, alarmed that the Covenant might overrun ODG A-331, overreacted and carpet-bombed the area, eliminating the Covenant advance as well as most of Charlie Company.

There were four survivors of Charlie Company that held their position until they met with the SPARTANs. The survivors were sent with several heavily wounded SPARTANs to a fall back position at [[Mechanite Mountain]], but all four Marines died from the Covenant, ending the UNSC Marine Corps's known involvement in the [[Battle of Reach]].

===[[Battle of Installation 04]]===
====Landfall====
A sizable [[Orbital Drop Shock Trooper]] special forces detachment and a standard [[Marine]] detachment was assigned to the {{UNSCShip|Pillar of Autumn}} for its intended operation to infiltrate [[Covenant]] High Command and kidnap a [[Prophet]]. This prophet was to be used as leverage for negotiating a peace treaty between the [[UNSC]] and the [[Covenant]]. However, the ambush over [[Threshold]] forced the ''[[UNSC Pillar of Autumn|Pillar of Autumn]]'' to crash land on the [[Forerunner]] installation also known as [[Installation 04]] ([[Alpha Halo]]). 
[[Image:Siege.jpg|right|thumb|Marines aboard the ''{{UNSCShip|Pillar of Autumn}}'' take cover from Covenant boarders behind [[Combat Barrier]]s.]]
The ''[[UNSC Pillar of Autumn|Pillar of Autumn]]'''s [[ODST]] detachment consisted of four 130-man companies: Companies A, B, C, and D, for a total of approximately 520 operators. During the Covenant boarding of the ''[[UNSC Pillar of Autumn|Pillar of Autumn]]'', they were assigned to defend the engine room of the warship against the boarding parties. They were extremely efficient in their defense, suffering only several dozen casualties while successfully holding off the Covenant at the two entrances to the massive engine chamber<ref>''[[Halo: The Flood]]'', page 33</ref>. However, the standard Marines did not fare as well in their defense, setting up multiple lines of defense around the periphery of the ''Pillar of Autumn'' and utilizing [[Combat Barrier]]s and urban combat techniques in the restrictive environment to hold off the enemy, which were [[Elite]]s and [[Grunt]]s. Ultimately, they were unsuccessful, and the Covenant managed to infiltrate many compartments of the warship before [[Captain]] [[Jacob Keyes]], commander of the ''Pillar of Autumn'', decided it was a lost cause to hold off superior numbers of attacking Covenant warships as well as internal boarders and ordered all hands to evacuate.<ref>''[[Halo: Combat Evolved]]'', ''[[Pillar of Autumn (Level)]]''</ref>.

Naval crewmen, standard Marines, and [[SPARTAN-117]] evacuated in the ship's [[Bumblebee]] life pods while the ODST companies utilized [[Human Entry Vehicle]]s. The landings, however, had numerous problems and killed dozens of UNSC Marines and Sailors alike. [[Major]] [[Antonio Silva]], the ODST Commander, ordered all surviving ODST units to secure a lightly-defended Covenant-held butte, which he turned into a coordinating home base for the UNSC resistance to come against the Covenant.  After securing it, the ODSTs worked to make it a strategically defensible point for the UNSC survivors. It was christened [[Alpha Base]] by Major Silva, who also ordered that all remaining UNSC forces to rendezvous there to make a stand. The Covenant launched a large vehicular [[Battle of Alpha Base|raid]] on Alpha Base of nearly a hundred [[Ghost]]s, but the 200 or so available ODSTs were able to repulse the poorly led assault.

The Covenant placed as high a priority on recovering [[UNSC]] life pods as the UNSC forces did.  Many of the successful landings were soon attacked by Covenant forces in an effort to minimize the number of Marines on the ring world. Individuals and teams such as [[SPARTAN-117]] and the [[Pelican]] ''[[Echo 419]]'' spent a considerable amount of time securing life pods throughout the installation, and regrouping the Marines to later lead the human resistance. [[Cortana]] was monitoring the Covenant Battlenet and discovered that [[Captain]] [[Jacob Keyes]] had made a safe landing of the ''[[UNSC Pillar of Autumn|Pillar of Autumn]]'' and had been captured by the [[Covenant]] ground forces. She also found that he was being held on the Covenant ship ''[[Truth and Reconciliation]]''.

====''Truth and Reconciliation''====
[[Image:Fitzgerald Shooting.jpg|right|thumb|[[UNSC]] Marines in a [[Warthog]] defend themselves against a [[Banshee]] after crash-landing.]]
[[Image:Halo-09.jpg|thumb|right|[[Fire Team Charlie]] secures the [[Gravity Lift]] of the ''[[Truth and Reconciliation]]'' while awaiting ''[[Echo 419]]'' to bring in further reinforcements.]]
[[SPARTAN-117]] led [[Fire Team Charlie]] to rescue Keyes from the grounded Covenant {{Class|CCS|Battlecruiser|}} ''[[Truth and Reconciliation]]''. They would set down a short distance from the Covenant battle cruiser, and then infiltrate through its [[Gravity Lift]].  From there, they would find Keyes, rescue him, and then evacuate.

Surprisingly, the plan went quite well. Despite a rather large Covenant force guarding the way into the ''[[Truth and Reconciliation]]'' and a pair of [[Hunters]] being deployed at the Gravity Lift (among other things), the approach was simple. From there, they were able to go up the Gravity Lift into the belly of the ''[[Truth and Reconciliation]]''. It was at this point that the Marines were ambushed by an Energy Sword wielding Elite. The Chief killed it, but unsure of what the device was at that time was unable to implement it against the Covenant. This was the UNSC's first encounter with new Covenant technology. It is worth noting that there were a few Type-25 Assault Gun Carriage or Wraiths in the hangers at that point also. The UNSC forces fiercely battled their way through alien corridors for fifteen minutes before reaching a spacious hangar bay. However, before they could continue, the Covenant were able to lock the doors on the Marines and [[John-117]], number of Marines, [[Cortana]] was able to use her computer countermeasures to force open a door that lead from the hangar to the bridge of the warship. Master Chief ordered his Marine comrades to wait in the bridge while he assaulted a Covenant brig, freeing Keyes and also three other captured Marines. However, by the time they returned to the bridge, [[Energy Sword]]-wielding [[Elites]] had slain the rest of the rescue team. They headed to the Hanger Bay for evacuation, but Covenant air patrols prevented their rescue. Instead, the team chose to hijack an enemy [[Spirit]] dropship that was laying dormant in the hangar bay, with Captain Keyes freed and secured<ref>''[[Halo: Combat Evolved]]'', ''[[The Truth and Reconciliation (Level)]]''</ref>.

Shortly afterwards, the UNSC Marine forces stationed at Alpha Base, under the command of Major Silva, decide to embark on a risky raid on the crashed hulk of the ''[[UNSC Pillar of Autumn|Pillar of Autumn]]'' to get much-needed supplies and ammunition, vehicular support, and fuel for the ferrying [[Pelican]] Drop ships. A small 62-man ODST force under the leadership of Lieutenant [[McKay]] raided the Covenant-patrolled crash site of the ''Pillar of Autumn'', using sniper fire to eliminate most of the defending [[Ghost]] attack vehicles and infantry, and then securing the ship with 10 casualties, securing much-needed supplies for the UNSC forces.<ref>''[[Halo: The Flood]]'', page 136</ref> However, the Covenant learned about this, and before McKay's force can return to Alpha Base and drop off the newly-seized supplies and vehicles that they had secured from the wreck of the ''Pillar of Autumn'', they were intercepted by a superior Covenant force in the rocky terrain. The tide of battle is turned to the UNSC's favor, however, by discipline, organization, and luck. The UNSC's four [[Scorpion Tank]]s used shell bombardment to destroy the attacking Covenant [[Type-25 Assault Gun Carriage|Wraith]]s, while the UNSC Warthogs fought off waves of assailing [[Banshee]] attack craft and [[Ghost]]s. The Covenant's aggressive tactics yielded no advantage, and the well-coordinated UNSC rocket units and a particularly bold feint by Second Lieutenant [[Oros]] destroyed the dozens of Covenant Banshees, and Marine sharpshooter [[Lance Corporal]] [[Jones]] took a serendipitous sniper rifle shot, killing a Covenant [[Elite]] [[Ado 'Mortumee|officer]], disorienting and fragmenting the Covenant resistance as UNSC forces plowed through the Covenant remnants.<ref>''[[Halo: The Flood]]'', page 160</ref>.

====The Flood====
{{Quote|Ahh... augh! Get [[Flood Infection Form|it]] off! Get it-augh!|[[Private]] [[Riley]], first known UNSC casualty to the [[Flood]]}}

Meanwhile, a [[Covenant]] [[Elite]], [['Qualomee]], surrendered to the UNSC and yielded intelligence about a Covenant arms cache in a faraway swamp. After Captain Keyes meets Major Silva and congratulates him and his [[ODST]]s for establishing Alpha Base for the UNSC, Keyes decides to lead a platoon of Marines under the leadership of [[Staff Sergeant]] [[Avery J. Johnson]] to secure this Covenant arms cache while [[Master Chief]] is ordered to a remote island where a [[Forerunner]] construct named the "[[Silent Cartographer]]" is stationed - a construct that is believed to hold an entire and fully-detailed map of Installation 04. Securing the intelligence would give the UNSC an inestimable edge in their resistance efforts.
[[Image:B30_01.jpg|right|thumb|[[Master Chief]] with a fire team of Marines on a Pelican inbound to the [[Silent Cartographer]]'s island.]]
[[Image:Marines2.jpg|right|thumb|A pair of [[Sergeant]] [[Pete Stacker (Marine)|Stacker]]'s Marines fight to secure an LZ after insertion on the beachheads on the cartographer island.]]
[[Image:4wiki.jpg|right|thumb|A Marine assists [[SPARTAN-117]] in a [[Warthog]] to find the Control Room.]]
[[Image:Kappus_tap.JPG|right|thumb|UNSC Marine [[Kappus]] opens a locked door in the Covenant "weapons cache", unwittingly unlocking the [[Flood]].]]
[[Image:343GS-Marine Run.jpg|thumb|right|Captain Keyes's second squad flees from the Flood-infested arms cache after meeting with [[Master Chief]].]]
Two Pelican Drop ships inserted two squads of Marines (lead by [[Gunnery Sergeant Waller]] and [[Sergeant]] [[Stacker]]) and [[Master Chief]] to an edge of the island. They were deployed under fire, but managed to secure a beachhead and a landing zone for the UNSC to land further reinforcements (including an [[M12 Warthog LRV]]). SPARTAN-117 and two Marines, PFC [[Hosky]] and an unnamed Female Marine [[corporal]], took the Warthog, driving it to a cliff that was the entrance to the facility that housed the Silent Cartographer. However, the Covenant knew that the UNSC was attempting to secure the intelligence, and locked the entrance way, forcing the trio to make a detour to a security substation, deactivating the locked door before finally being able to tunnel their way through the Covenant defenses stationed inside the subterranean facility and retrieving the intelligence.

The surviving Marines still waiting on the landing zone were scheduled to be reinforced by Pelican [[Bravo 22]] when it was shot down by ground arsenal. Shortly afterwards, a pair of [[Spirit]] drop ships converged on the Marines by the landing zone, overwhelming them on the exposed terrain of the beachhead while SPARTAN-117 was still within the bowels of the underground facility. The forces on the beachhead are presumed dead. The lack of a UNSC-held landing zone on the surface of the island meant that ''Echo 419'' could not extract [[Master Chief]] and his vital intelligence. However, [[Cortana]] found that there was a massively honeycombed system of massive open corridors that permeate the ground of Installation 04, allowing a vehicle that entered the system to travel essentially anywhere undetected. ''[[Echo 419]]'' was able to slip into the system and rescue [[Master Chief]].  Using this system, [[Master Chief]] was able to be transported to the installation's Control Room<ref>''[[Halo: Combat Evolved]]'', ''[[The Silent Cartographer (Level)]]''</ref>.

Captain Keyes's team, meanwhile, landed near the site of the supposed "weapons cache".  The two Marine teams cleared the Covenant defenses and began to search the underground facility where the arms were supposedly stored. One team stayed back while the other team, led by [[Staff Sergeant]] [[Johnson]], searched the facility. Eventually, they ran across a door that had been electronically locked by the Covenant. Despite the protest of the technician, [[Captain Keyes]] ordered the door to be unlocked to gain access. Shortly after entering the room, however, the advance team, including Captain Keyes, was attacked by parasitic organisms called [[Flood]]. [[Staff Sergeant]] [[Johnson]] managed to escape after the Flood [[Infection Forms]] took over his fellow Marines, that infection did not incur due to his deteriorated nervous system, courtesy of [[Boren's Syndrome]].  [[Private]] [[Bisenti]] would also survive the attack but is speculated to have died when [[Spartan 117]] blew up [[Installation 04]]. Due to a failed infection attempt, [[Private First Class]] [[Jenkins]] was infected but had control over his consciousness and some body functions. [[Jenkins]] was later captured and interrogated by UNSC forces.

[[Cortana]] had already learned of the threat the Flood was and sent [[SPARTAN-117]] to save Keyes.  However, the Spartan would only find Jenkins' helmet and it's mission log.  When he was on the way to the evacuation site, he fought against Flood Infection and Combat Forms of both Covenant Elite and human Marine form, then ran into a surviving squad of  Marines and began retreating with them to a nearby structure, whilst being assaulted by Flood Combat forms. After securing an LZ for dropship ''Echo 419'', he would then disappear after encountering [[343 Guilty Spark (Monitor)|343 Guilty Spark]].<ref>''[[Halo: Combat Evolved]]'', ''[[343 Guilty Spark (Level)]]''</ref>. 

Meanwhile, Alpha Base came under heavy attack from a Covenant force. The Covenant had identified that SPARTAN-117 was responsible for the majority of the hundreds of casualties during the raid on the ''[[Truth and Reconciliation]]'', and an ambitious [[Special Operations Elite]] named [[Zuka 'Zamamee]] was tasked with leading a platoon of Special Operations Elites into the bowel of Alpha Base to assassinate the [[SPARTAN-II|Demon]] while a much larger Covenant force distracted the UNSC defenders. Using a captured Pelican drop ship, [[Charlie 217]], 'Zamamee infiltrated the UNSC HQ, but SPARTAN-117 was nowhere to be found. Meanwhile, [[Spirit]] drop ships hit the UNSC defenses, but are thrown back by massive amounts of sniper rifle fire and several [[Scorpion Tank]]s. Furthermore, the ODSTs organize several hunter-killer teams to re-secure the HQ, murdering all the Special Operations Elites save 'Zamamee, who was able to rescue a captive Grunt named [[Yayap]] and escape with Yayap in a [[Banshee]] fighter<ref>''[[Halo: The Flood]]'', page 220</ref>.

====Containment====
While [[SPARTAN-117]] journeyed through various areas in [[Installation 04]], [[Cortana]] was able to briefly contact [[Alpha Base]], informing them that [[SPARTAN-117]] will use the ''[[UNSC Pillar of Autumn|Pillar of Autumn]]'''s reactors to trigger a thermonuclear explosion that would destroy [[Installation 04]]. However, the explosion would kill all life on the ring world if the UNSC forces failed to escape before the detonation.  [[Major]] [[Silva]] came up with a daring plan: to recapture the damaged ''[[Truth and Reconciliation]]'', already taken to launch readiness by a [[Covenant]] repair team, and to use it to escape the ring while [[SPARTAN-117]] sets off the delayed thermonuclear reaction and escapes as well. Afterwards, [[SPARTAN-117]] will rendezvous with the UNSC-controlled ''Truth and Reconciliation'' and then they will return to [[Earth]], heralding a glorious victory for the UNSC: a superweapon destroyed, a [[Covenant]] armada annihilated, and the first [[Covenant]] warship ever captured. 

However, this plan was not perfect. [[Alpha Base]]'s contingent learned of the [[Flood]] as a brief skirmish with nearby [[Covenant]] patrols led to an exaggerated battle as the [[Flood]] attacked, and the [[UNSC]] personnel were mostly horrified by the [[Flood]]'s combat potential and viciousness.<ref>''[[Halo: The Flood]]'', page 251</ref> After it was learned that Flood were aboard the ''Truth and Reconciliation'', ODST [[Lieutenant]] [[McKay]] and UNSC AI [[Wellsley]] were convinced that the UNSC survivors should not risk severe casualties boarding a [[Flood]]-infested [[starship]]... and even if they prevail and brought the [[warship]] to [[Earth]], if any [[Flood]] managed to invade [[Earth]], the planet would fall<ref>''[[Halo: The Flood]]'', page 317</ref><ref>''[[Halo: The Flood]]'', page 331</ref>. However, [[Silva]], the commanding officer of all of [[Alpha Base]]'s forces after [[Keyes]]'s tragic death, demured, and instead assaulted the ''Truth and Reconciliation'', with his [[ODST]] special forces operators securing the ship with minimal casualties and the non-combat personnel in tow. Surviving senior naval officers from the ''Pillar of Autumn'' were sent in after the [[ODST]]s deem the warship as "secure", and they moved swiftly to under see last-minute repairs to the ''Truth and Reconciliation'' before it took off.

However, [[McKay]] still held doubt - even if the ''Truth and Reconciliation'' took off successfully and reached [[Earth]] without incidence, the epidemiological threat of the [[Flood]] meant that if even one parasite managed to infect a [[human]] on [[Earth]], it would be a disaster of a galactic scale. [[McKay]], in conscience, made the decision to damage the ''Truth and Reconciliation'''s reactors and destroy the warship, killing herself and all 312 [[UNSC]] personnel and surviving [[Flood]] beings on board<ref>''[[Halo: The Flood]]'', page 332</ref>, thereby destroying nearly all of the [[UNSC]] presence on the ring.

====Escape====
While almost all of [[Alpha Base]]'s personnel were eliminated in the tragic self-detonation, [[Avery J. Johnson]] did not make it onto the ''[[Truth and Reconciliation]]'' after surviving the [[Flood]] attack.  He was able to join three other UNSC personnel that were, likewise, not aboard the ''Truth and Reconciliation'': [[Office of Naval Intelligence]] [[Lieutenant]] [[Elias Haverson]], ODST [[Corporal]] [[Locklear]], and [[Warrant Officer]] [[Sheila Polaski]]. Together, the four escaped [[Installation 04]] in a [[Pelican Dropship]]<ref>''[[Halo: First Strike]]'', page 48</ref> before [[SPARTAN-117]] set off the thermonuclear detonation, himself escaping in a [[C709 Longsword-class Starfighter|C709 ''Longsword''-class Starfighter]]<ref>''[[Halo: Combat Evolved]]'', ''[[The Maw (Level)]]''</ref>.

After [[Installation 04]]'s destruction, [[Cortana]] conducted a scan of the interstellar debris of [[Installation 04]], and found an echo of [[Polaski]]'s [[dropship]]. [[SPARTAN-117]] was able to link up with the four other [[UNSC]] survivors of the cataclysm, but seven [[Covenant]] warships: six [[Covenant Cruiser]]s and one 3-kilometer [[Covenant Flagship]], entered the system and opened fire at the fighter and the [[Pelican]]. [[SPARTAN-117]] ordered everyone into the [[Longsword]] while the [[Pelican]] was sent ahead as bait, drawing [[plasma]] fire from the [[Covenant]] starships while [[Cortana]] remotely hacked into the [[Covenant]] task force's [[Battlenet]], causing electronic mayhem that temporarily stunned the weapons aboard the warships while the [[Longsword]], with [[SPARTAN-117]], [[Johnson]], [[Locklear]], [[Polaski]], and [[Haverson]] on board, slipped into the hangar of the [[Covenant]] [[Flagship]]<ref>''[[Halo: First Strike]]'', page 58</ref>.
[[Image:Marine.png|thumb|right|[[Corporal]] [[Locklear]] fights the [[Covenant]] with an [[MA5B Assault Rifle]] in the brief battle inside the ''[[Ascendant Justice]]''.]]
The small group of unprepared [[UNSC]] warriors fought through [[Elite]] defenders while [[Cortana]] slipped into the [[Covenant]] [[Flagship]]'s computer systems from a fiber optic port, and proceeded to drain atmosphere from most segments of the ship, asphyxiating most of the [[Covenant]] guards. However, the bridge's crew still remained alive, and sealed the doors to the bridge, barricading themselves from the [[UNSC]] attackers. This measure was ultimately futile: [[SPARTAN-117]] used a [[plasma grenade]] to electromagnetically scramble the locks to the doors, and the [[UNSC]] forces seized the understaffed bridge with minor difficulties. [[SPARTAN-117]]'s personal energy [[shield]] failed just as an [[Energy Sword]]-wielding [[Zealot]] appeared. [[SPARTAN-117]] nearly had his arm amputated in the resulting wrestle, but Marines [[Johnson]] and [[Locklear]] were able to severely wound the [[Zealot]], before throwing him into an escape pod and launching it<ref>''[[Halo: First Strike]]'', page 74</ref>.

[[Cortana]] interfaced with the bridge's navigational controls to let the now [[UNSC]]-controlled [[flagship]], ''[[Ascendant Justice]]'', flee from the system, but a [[Covenant]] AI countered her, physically disabling the [[Slipspace]] drive of the ''[[Ascendant Justice]]'' and preventing [[Cortana]] from executing a jump out of the system before the six other Covenant Cruisers vaporize the flagship. [[SPARTAN-117]], however, made a journey through the damaged warship to kill the [[Grunt]]s guarding the disabled [[Shaw-Fujikawa Translight Engine|Slipspace drive]], and then forces a [[Covenant]] [[Engineer]] to repair the drive, allowing [[Cortana]] to program the ''[[Ascendant Justice]]'' to jump from the system, just barely surviving the bombardment of the six [[Covenant]] [[Cruiser]]s, thus ending the [[UNSC]] retreat from the war-torn system.<ref>''[[Halo: First Strike]]'', page 87</ref>

===[[First Battle of Earth]]===
[[Image:Hotelz2rw.jpg|right|thumb|[[Hotel Zanzibar]] defended by a light Marine fireteam.]]
[[Image:DSC00123.JPG.jpg|right|thumb|Marines of [["A" Company]] fire at the Scarab walker with a .30-caliber machine gun.]] 
[[Image:Scarabcannon.jpg|right|thumb|The [[Scarab]] destroys a [[UNSC Marine Corps]] [[Scorpion Tank]] in a single shot.]]
[[Image:DSC00124.JPG|right|thumb|[["A" Company]] of the [[405th Marine Infantry Division|405<sup>th</sup> Marine Division]] before attacking the [[Scarab]] walker.]]

{{Main|First Battle of Earth}}

{{Quote|[[UNSC In Amber Clad|We're]] taking [[First Battle of Earth|this fight]] to the [[Earth|surface]].|[[Commander]] [[Miranda Keyes]]}} 

The [[UNSC]] Marine Corps remained in force on [[Earth]] and its geosynchronous [[Orbital Defense Platform]]s, and were thus mostly prepared to repulse a relatively small [[Covenant]] invasion when fifteen [[Covenant]] capital warships, two [[Assault Carrier]]s and thirteen [[Covenant Cruiser]]s, entered the Sol System.

Because the large number of orbital [[Magnetic Accelerator Cannons]] made it almost impossible for any of the [[Covenant]] warships to reach [[Earth]] unscathed, the [[Covenant]] sent [[Covenant Boarding Craft|boarding craft]] to board numerous [[Orbital Defense Platforms]]. The boarders swiftly penetrated the platform's infantry defenders and set bombs in the core of the stations and then detonated them, destroying the defense station inside-out with minimal losses. ''[[Malta Station]]'' and ''[[Athens Station]]'' fell almost immediately to the internal sabotaging.

[[Covenant]] forces invaded ''[[Cairo Station]]'' as well, the command center for [[UNSC]] fleet operations during the battle. The crew of the ''[[Cairo]]'' held out longer, albeit with heavy casualties, and [[Marines]] and crewmen fought a coordinated holding action, trying to force the boarders out of the peripheral hangars and the intermediate common rooms, but their defenses were penetrated by a small force of [[Elite]]s and [[Grunt]]s that planted a bomb in the Fire Control Center of ''[[Cairo Station]]''. Only [[SPARTAN-117]]'s timely reinforcement of the [[Marine]] garrison and his assault on the Fire Control Center managed to '''disarm''' the bomb in time, thus saving ''[[Cairo Station]]'' from destruction.<ref>''[[Halo 2]]'', ''[[Cairo Station (Level)]]''</ref>. John then proceeded to send the bomb to another Covenant ship, utterly destroying it.

However, despite the fact that ''[[Cairo Station]]'' and hundreds of others of [[Orbital Defense Platforms]] still stood, the loss of the ''[[Malta]]'' and ''[[Athens]]'' allowed a [[Covenant]] [[Assault Carrier]] to penetrate the [[UNSC]] Navy's defensive web around [[Earth]], and this [[Assault Carrier]] attacked [[New Mombasa]], [[Africa]]. 

However, the [[405th Marine Infantry Division|405<sup>th</sup> Marine Infantry Division]], some of whose elements were stationed in [[Mombasa]], [[Kenya]] at the time, were able to battle against the [[Covenant]] as the [[Assault Carrier]] landed [[Phantom]]s, [[Orbital Insertion Pod]]s, and used its [[Gravity Lift]] to directly deploy reinforcements. Furthermore, the [[UNSC In Amber Clad|In Amber Clad]] was also able to use its [[Pelican]]s to deploy [[Marines]], vehicles, and equipment to assist the 405<sup>th</sup> Marine Division. 

The ''[[UNSC In Amber Clad|In Amber Clad]]'' sent three [[Pelican Dropships]] to reinforce and to drop off [[Marine]] and [[ODST]] fire teams at [[Grid Kilo 23]], where [[SPARTAN-117]] and [[Johnson]] would lead a coordinated [[Marine]] assault to liberate the [[Covenant]]-contested city center, when the [[Pelicans]] were unexpectedly attacked by a [[Scarab]] en route to their landing zone. Two of the [[Pelicans]] were forced to break off when one of the ''[[UNSC In Amber Clad|In Amber Clad]]'''s [[Pelicans]], which contained [[SPARTAN-117]] and [[Sergeant Johnson]], crashed into a building. 

Miraculously, everyone aboard the Pelican except the pilot survived, and [[SPARTAN-117]] was able to rally the Marine passengers, holding a nearby battle-damaged building against multiple Covenant attacks until the Marines could be evacuated at a nearby clearing. 

Meanwhile, SPARTAN-117 proceeded to relieve a small ODST force, under the command of [[Gunnery Sergeant]] [[Pete Stacker]], at [[Hotel Zanzibar]], and then fought through a Covenant-controlled tunneled highway where the [[Covenant]] were using the tunnel as a supply route.<ref>[[Outskirts(level)]]</ref>. 

However, the Scarab brushed aside Marine defenses, walking over the highway, and then past a large bridge and into the midsection's of the city completely unopposed by Marine small arms fire<ref>''[[Halo 2]]'', ''[[Outskirts (Level)]]''</ref>.

[[SPARTAN-117]] and a small team of Marines pursued the lumbering walker, fighting through long segments of Covenant-controlled city locations until reaching the city center, where [["A" Company]] of the [[77th Marine Regiment|77<sup>th</sup> Marine Regiment]] defended against waves of Covenant [[Ghost]]s, [[Type-25 Assault Gun Carriage|Wraith]]s, and [[Phantom]]s in a fortified industrial building. 

Completely undeterred by UNSC Marine Corps [[Scorpion Tank]]s or machine guns, the Scarab too brushed aside "A" Company in its fortified building, until it was caught in a nearby canal system and physically trapped. Pelicans commenced air strikes on the trapped walker, but the armor was barely scarred, and there was no other choice but to board the Scarab itself and destroy internally. While "A" Company's remnants provided suppressive fire, [[SPARTAN-117]] boarded the enemy walker when the Scarab was stuck by a bridge, killing its crew (numerous Grunts and Elites) and destroying it<ref>''[[Halo 2]]'', ''[[Metropolis (Level)]]''</ref>.

===[[Battle of Installation 05]]===
{{Main|Battle of Installation 05}}

{{Quote|[[Cortana]]? What exactly am I looking at?|[[Commander Miranda Keyes]]}}
{{Quote|[[Installation 05|That]]...is another [[The Halos|Halo]].|[[Cortana]]}}
{{Quote|Say what?!|[[Sergeant Major]] [[Avery Johnson|Avery J. Johnson]]}}
[[Image:Hevstohalo05.jpg|right|thumb|[[Human Entry Vehicle]]s from the {{UNSCShip|In Amber Clad}} insert into the atmosphere of [[Installation 05]].]]

After the [[Slipspace]] cataclysm over [[Mombasa]] involving the [[Prophet of Regret]]'s [[Assault Carrier]], [[UNSC In Amber Clad|In Amber Clad]] pursued the Prophet of Regret's carrier through [[Slipspace]] to [[Installation 05]] (Delta Halo), where Regret was determined to sermonize and then activate the ring world and bring about [[The Great Journey]] to all of the [[Covenant]] and lead them to a believed transcendence. 

While the carrier sent [[Phantom]] drop ships to the surface to land the [[Covenant Army]] in the immediate area and to allow Regret to begin his religious ceremony in a Forerunner temple before activating the ring, the ''In Amber Clad'' passed over the approximate position where Regret's temple was, deploying ten [[Human Entry Vehicle]]s, and shortly afterward, a flight of Pelican Dropships.

While only a handful of HEV pods survived the insertion, the surviving ones contained [[SPARTAN-117]] and several heavily armed [[Orbital Drop Shock Trooper]]s. Together, they cleared a small area of [[Shielded Plasma Cannon]]s and a small group of Covenant soldiers, establishing an LZ for a Pelican Drop ship to deploy an [[M12 Warthog LRV]] and another pair of ODST operators. 

SPARTAN-117 took the Warthog, and with the help of the ODSTs, fought through a Covenant-controlled bridge before another Pelican deployed a M808B Scorpion MBT that provided extra firepower for a UNSC offensive to push through two large Forerunner temple ruins, and to neutralize the Wraith where yet a third Pelican from the ''In Amber Clad'' dropped off resupply drop pods and Marine reinforcements. 

After battling through a ravine entrenched by aerial [[Yanme'e|Drone]]s and [[Jackal Sniper]]s, the UNSC force reached a small Forerunner temple, where SPARTAN-117 and two remaining Marines fought off a pair of [[Honor Guard Elite]]s<ref>''[[Halo 2]]'', ''[[Delta Halo (Level)]]''</ref> before continuing onwards through a series of closed temples before reaching an open circular platform where a fourth Pelican was scheduled to air-drop additional armaments. 

However, before that could happen, SPARTAN-117 and whatever surviving Marines were attacked by an airborne [[Phantom]] dropship that deployed two heavy [[Hunter]] warriors that savagely assailed the UNSC personnel before they were fought off and the fourth Pelican arrived to bring [[BR55 Battle Rifle]]s, Sniper Rifles, and [[M19 SSM Rocket Launcher]]s. SPARTAN-117 continued to take a gondola from the open platform, fighting off enemy [[Banshee]] fighters and [[Ranger Elite]]s to reach a series of submerged temple structures and finally another gondola to the temple where Regret was sermonizing.

SPARTAN-117 and his Marines began fighting off [[Energy Sword]]-armed [[Honor Guard Elite]]s, managed to assassinate the Prophet of Regret before the [[Prophet of Truth]] and [[Prophet of Mercy]] ordered an Assault Carrier to use an [[Energy Projector]] to vaporize the temple in a vain attempt to kill the "Demon", afterward which contact was lost with SPARTAN-117 and whatever remaining Marines that were accompanying him at the time.

Meanwhile, at ''[[High Charity]]'', the [[Changing of the Guard]] occurred, and the [[Arbiter (Character)|Arbiter]] was deployed to the [[Sentinel Wall]]<ref>''[[The Official Halo 2 Strategy Guide]]'', page 118</ref> to deactivate the containment shield that prevented any being from journeying to the [[Library]] and retrieving the [[Index]]. After the Containment Shield was deactivated, apparently a company-sized Marine unit was sent to the Flood-Infested Wall<ref>''[[The Official Halo 2 Strategy Guide]]'', page 115</ref><ref>''[[Halo 2]]'', ''[[Sacred Icon (Level)]]''</ref> to try to make their way to the Library, but were overwhelmed by the Flood and assimilated. 

However, while the Arbiter punched through heavy Flood defenses surrounding the Library, the UNSC tried again to attack the [[Library]] and secure the [[Index]] to ensure that the Covenant would not use it to activate Installation 05 and cleanse the galaxy of sentient life in their misguided religious quest. While the Arbiter cleaned out the Flood infestation barring way to the Library, the UNSC were able to slip a small force of Marines directly next to the Forerunner structure, who managed to infiltrate it, but took casualties from [[Flood infection form]]s. 

At the end, only [[Miranda Keyes]] and [[Avery Johnson]] survived, but while Commander Keyes secured the Index, the Arbiter managed to race into the Library, incapacitating Perez and MacKenzie before launching a sneak attack on Johnson and Keyes, knocking them both unconscious before securing the Index for the Covenant<ref>''[[Halo 2]]'', ''[[Quarantine Zone (Level)|Quarantine Zone]]''</ref>.

===[[Battle of High Charity]]===
{{Main|Battle of High Charity}}

However, [[Spartan-117]] had survived the Covenant vaporization of Regret's Temple, but had a more insidious fate: deceived by the Flood overlord creature known as the [[Gravemind]], he became the Flood's pawn, being teleported to ''[[High Charity]]'' in an attempt to battle through legions of Covenant troops to capture or kill the [[Prophet of Truth]] and secure the Index to ensure that Truth would not activate Halo. 

Early on during the Battle of ''High Charity'', however, [[Cortana]] detected the [[CNI]] wave signatures of several UNSC Marines inside the bowels of ''High Charity''. SPARTAN-117 took a short detour, launching an attack on a four-story Covenant detention facility and rescuing five Marine prisoners from a pair of heavily guarded Covenant detention blocks, who aided him in his battles through ''High Charity''. 

In the end, however, none of the Marines survived (even if you some how complete the level with some of them still alive, they won't be there in the next Master Chief level), and the [[Prophet of Truth]] escaped from SPARTAN-117's grasp, fleeing in a Phantom drop ship while [[Tartarus]], Chieftain of the Brutes, took the imprisoned Keyes and Johnson, along with a cohort of [[Honor Guard Brute]]s, in two separate [[Phantom]]s to Installation 05, where Tartarus planned to use the Index to activate Halo at the Control Room of Installation 05<ref>''[[Halo 2]]'', ''[[Gravemind (Level)]]''</ref>.

Meanwhile, the ''In Amber Clad'' had not fared well after Keyes's team's departure from the frigate. Flood forces managed to storm aboard by use of crashed [[Pelicans]], killing the human crew and using their unprecedented sentience to crew the ship. They managed to crash it onto a high tower on ''High Charity'', spreading Flood into the Covenant planetoids. Pelican dropships provided the Flood with extensive routes to invade ''High Charity''. 

A number of its crew were assimilated into the insular of the parasite, fighting against SPARTAN-117 as the Master Chief battled through a Flood-infested ''High Charity'' to secure access to the [[Forerunner Ship]]<ref>''[[Halo 2]]'', ''[[High Charity (Level)]]''</ref>.

While Tartarus took the Index and Miranda Keyes in one Phantom to the Control Room, the other Phantom, carrying Johnson, diverted its route. When arrived with two other captured Marines, the Arbiter arrived and with the distraction, the Marines and himself managed to slip through to an inactive [[Scarab]] walker while two nearby Marines, most likely [[Sergeant Stacker]] and [[Sergeant Banks]], fought off a large pack of [[Brute Captain]]s with [[Plasma Pistol]]s. These two Marines were saved when the Arbiter arrived, slaying the Brutes. 

However, Johnson pointed the Scarab's main cannon at the Arbiter...but not in bad will. The Arbiter and Johnson made a truce. Johnson would use the main cannon of the Scarab to punch a hole in the surface of the Control Room while the Arbiter would charge in with a [[Banshee]] and defeat Brute Captains and Brute Honor Guards before confronting [[Tartarus]] while Johnson would dismount from the Scarab, joining a large number of [[Covenant Separatist]] [[Councilors]], [[Zealots]], and [[Special Operation Elite]]s in aiding the Arbiter to kill Tartarus and prevent him from using the Index to activate Halo.

However, Tartarus put up a significant resistance, and despite being heavily outnumbered by the Arbiter's Elite comrades, used his personal energy shield and the gargantuan [[Fist of Rukt]] to defend himself. In the end, however, Tartarus was unsuccessful. 

Johnson used his exceptional marksmanship to take down Tartarus's powerful shields from afar with a [[Particle Beam Rifle]] while the Arbiter and his allies attacked the unshielded Tartarus, finally killing him and bringing an end to the Chieftain of the Brutes and preventing the firing of the Halos, terminating the UNSC Marine Corps's involvement at Installation 05.

===[[Second Battle of Earth]]===
{{Main|Second Battle of Earth}}
[[Image:Halo 3 Marines.png|right|thumb|Four Marines take cover in the jungles around [[Voi]].]]

When the Arbiter arrived on Earth with [[Commander Miranda Keyes]] and [[Sergeant Major Avery J. Johnson]], he requested a truce between the Sangheili and Human races. Knowing the desperate situation for the human race being close to extinction from the remainder of the Covenant, the Arbiter united the Separatists and the Human Race.

The UNSC Marine Corps had a substantial involvement in the defense of Earth during the Second Battle of Earth, being the majority of the UNSC's ground defenses when the Covenant landed on Earth in multiple locations, which included the continent of [[Africa]].

A scattered Marine presence appeared to remain in force in the immediate vicinity of [[New Mombasa]], where a [[Slipspace]] disaster wiped off a significant number of Marine assets, including a portion of the [[405th Marine Infantry Division|405<sup>th</sup> Marine Infantry Division]]. 
[[Image:UNSC Marine.jpg|right|thumb|A Marine in the UNSC base of [[Crow's Nest (Base)|Crow's Nest.]]]]

[[Marine]] forces managed to hold out in an underground base, waging a guerrilla war against the [[Covenant]] occupiers of East Africa for some time before the [[Master Chief]]'s arrival from on board the [[Forerunner Dreadnought]] <ref>Sierra 117 (level)</ref>. After his recovery, Marine forces prepared to launch an offensive against the Covenant and reach what they thought to be the [[Installation 00|Ark]]. Unfortunately, the Covenant found them first, and assaulted the base with heavy numbers of infantry. The Marines, Master Chief, and the Arbiter managed to fend them off long enough to evacuate the remainder of the survivors, and destroyed the base rather than let the Covenant learn of their plan<ref>Crows Nest (level)</ref> - the Master Chief personally led a small number of Marines along the Tsavo Highway, penetrating through numerous blockades and passing patrols of [[Type-25 Rapid Assault Vehicle|Choppers]] and [[Wraiths]], eventually reaching the town of Voi<ref>Tsavo Highway (level)</ref>.
[[Image:58478962-Full.jpg|thumb|Marines supported by [[Voi Factory Workers|armed civilians]] during the [[Battle of Voi]].]]
Once at Voi, the Master Chief and the Marines began their operation - destroying all anti-air emplacements, in order to allow Pelican drop ships to insert more UNSC forces, including the Arbiter. One emplacement from a perimeter of heavy [[Covenant Air Artillery|Anti-Air Artillery]] was disabled, allowing UNSC [[C709 Longsword-class Interceptor|Longsword]] Fighters and [[UNSC Frigate|Frigates]] to attack the [[Forerunner Dreadnought]]. The [[Prophet of Truth]], however, activated a portal over the "Ark," leading to the true facility - and a Covenant Cruiser made a pinpoint slipspace jump in-atmosphere above Voi, infected by the [[Flood]]
[[Image:Marine Ambush.jpg|thumb|Four Marines near [[Tsavo Highway (Highway)|Tsavo Highway]].]]
The [[Unnamed Marine Lieutenant|Marine Lieutenant]] commanding forces in Voi soon was forced into a brutal firefight against the Flood, in which he and all of the Marines in his command post were infected, except for [[Suicidal Marine|a single survivor]].

Spartan-117, having destroyed the AA Gun battery, reentered Voi with the Arbiter, and began attacking the Flood and rescuing Marine survivors. Despite his best efforts, only six Marines (plus the Sergeant from the loading ramp and the additional marines from his squad), not counting the traumatized survivor of the raid on the CP or, were rescued. About midway to the crash site of the Flood-controlled ship, the unlikely rescuers of the humans, the First Sangheilian Fleet under [[Rtas 'Vadum]], arrived, and deployed [[Special Operations Sangheili]] to assist in the evacuation of John-117 and his Marine squad, and glassing of all infected areas. The Marines that the Chief had been evacuated, and were transported to the Forward Unto Dawn, thus ending major UNSC Marine corp operations in this area.

===[[Battle of Installation 00]]===
{{Main|Battle of Installation 00}}
====Exploration and Touchdown====
{{quote|All armor form up, hit 'em where it hurts!|[[Gunnery Sergeant]] [[Pete Stacker]], leading a Scorpion platoon on the Ark|The Ark (level)}}
[[Image:7thHelljumpers.jpg|thumb|ODSTs from the [[7th Orbital Drop Shock Trooper Battalion|7th Battalion]] advance along the [[Ark]].]]
[[Image:1208308468 Charge by zaku0909.jpg|thumb|The ODSTs are a special branch of the UNSC Marine Corps.]]
[[Image:Corporal Wu.jpg|thumb|A Marine sharpshooter on the Ark.]]
Following negotiations between Admiral Hood and [[Rtas 'Vadum]] onboard the [[Sangheili]] flagship [[Shadow of Intent]], it was agreed that the Sangheili Fleet, as well as the Forward Unto Dawn and her Marine complement, would follow [[Truth]] through the Portal to the [[Ark]], after realizing the magnitude of the [[Flood]] threat to all of the galaxy's sentient life and the importance of retrieving the [[UNSC]] A.I. [[Cortana]].

Upon emerging from the Portal, the Sangheili fleet encountered a [[Jiralhanae]] fleet three times their size. With 'Vadum's ships holding the line against Truth's fleet, Spartan-117, the Arbiter, and a Marine-ODST task force under Sergeants [[Avery Johnson]], [[Reynolds]], and [[Pete Stacker]] landed on the Ark.

[[Spartan-117]]'s first objective was to clear AA defenses so Commander Keyes could set down the Dawn; he was dropped off with four ODSTs near the first Covenant battery. They proceeded to knock it out, and linked up with two Marines whose Pelican had been shot down. The impromptu assault team hijacked a Jiralhanae Prowler, commandeered a Mongoose from the wreck of the Pelican, and headed out to the last AA battery. Once it was destroyed, Commander Keyes set down the Dawn, and deployed Bravo Team, an armored unit of three Scorpions and a chain-gun warthog under Gunnery Sergeant Stacker, as well as 343 Guilty Spark.

The armored platoon forged ahead, and managed to penetrate a wall separating Spartan-117 from his objective: a Cartographer similar to the one found on [[Installation 04]]. However, a Scarab, a Phantom, and several Wraith tanks were in the way. Bravo Team managed to skillfully bludgeon their way through the Covenant defenses, and Spartan-117 managed to arrive at the Cartographer building, discovering that Truth was holed up in a Forerunner Citadel in the center of the Ark.

====Pathfinding and Confrontation====
Upon the discovery of Truth's location, a flight of five [[Pelican]]s and two Separatist [[Phantom]]s made way to the Citadel. They split up into three groups; the Arbiter led his two Phantoms' worth of Elites, Avery Johnson led a duo of Pelicans filled with Marines, and the Master Chief took another two Pelicans holding [[ODST]]s. Their goal was to split up and quickly deactivate the three shield generators surrounding the Citadel. [[Miranda Keyes]] held back and waited to give the [[Master Chief]]'s team support, fearful of the Anti-Air Wraith guarding their insertion point. Her fears were justified when one of the two Pelicans of the Master Chief's team was shot down. The remaining bird landed the Chief and just three ODSTs to take out the [[Brute]] position and disable the Wraith. Through much hardship and desperation they did just that, and awaited Miranda Keyes' reinforcements of three more Marines, a [[Warthog]] and a [[Mongoose]]. The mounted strike force then fought their way to the interior of the island, towards one of the three generators the battle group was tasked with taking out.

The Master Chief and his team proceeded inside the generator complex, fighting a myriad of loyalist Covenant along the way. The Chief made his way up to the control center, slew a pack of Brutes including a [[Brute Chieftain]], and deactivated the generator. Approximately that same moment, the Arbiter and his Elites deactivated their generator as well. Expecting the third station to fall along with them, Miranda and the Chief were shocked to hear that Johnson's team of Marines was being overwhelmed by Brute reinforcements and were forced to fall back. Keyes rallied the other two strike teams and ordered them to finish the job that Johnson's team had started. 

The team being led by the Master Chief sped back down to their original landing zone, and were picked up by a flight of [[Hornet]]s. Assisted by the remaining two Pelicans, they all battled their way through stiff Covenant air resistance and saw the massive enemy force that had understandingly subdued the now apparently vanished Johnson's team. A vicious landing operation commenced, and the whole cliff side station was violently cleared for the Master Chief and remaining Elites (including the Arbiter) to storm the generator complex and deactivate the final power source. 

As the shield went down, a fully Flood-consumed [[High Charity]] burst out of slip-space (presumably from the portal on Earth) onto the Ark. A number of pieces of debris smashed through the Elites cruiser, severely damaging it. A chunk of infested debris also smashed through the complex, and the Chief fought the Flood as he got back outside to the deployment zone. 

Upon her arrival, Keyes had delivered a [[Scorpion]], a [[Gauss Warthog]], and a few [[Mongooses]] for him to use as he led the remaining Marine ground force and a handful of Elites to the interior of the island and begin the siege of the Citadel. The mounted and heavily armed task force battled their way down the Covenant fortified cliff side and was then met by a terrifying welcome party of two [[Scarab]] tanks. The remaining airborne force of Pelicans and Hornets assisted the Chief's team as they fiercely fought and destroyed this last line of defense. 

The Master Chief and the Arbiter then proceeded into the Citadel to rescue Johnson and kill the Prophet of Truth, but only made it after Miranda Keyes' desperate rescue attempt. Johnson escaped using Miranda's Pelican and returned to [[Forward Unto Dawn]], and the Master Chief and the Arbiter had to fight their way out, escaping the Flood and the Covenant. The remaining Marines and Elites were withdrawn to the [[Shadow of Intent]] as the Master Chief ventured into the remains of High Charity in search of Cortana.

Later, Avery Johnson's exploits aided in the final destruction of the reborn Installation 04 and the Flood, giving his life for Humanity and the Arbiter along the way.

As [[Forward Unto Dawn]] crash-landed into water mass on Earth, Marines (likely those that did not travel to the Ark, or had remained behind with [[Lord Hood]]) helped the Arbiter out of the wreck, and also participated in the memorial ceremony near the Ark Portal. It is likely that Marines were involved in peacekeeping and aid missions on Earth, or sent into space to battle against any remaining Covenant Loyalist forces.

==Uniform==
===Dress Uniform===
The Marine Corps Dress Uniforms are similar to those worn by their 20th and 21st Century predecessors in the [[United States Marine Corps]]. Instead of the Eagle, Globe, and Anchor worn by U.S. Marines, the [[UNSC]] uses their Eagle Insignia on their collars. Furthermore, white jackets and blue trousers are worn instead of the all-blue uniforms of the United States Marines.<ref>''[[Halo 2]]'', ''[[Cairo Station (Level)|Cairo Station]]''</ref> However, in [[2525]], the uniform apparently consisted of a blue jacket and trousers, similar to that of the USMC.<ref>''[[Halo: Contact Harvest]]''</ref>
===Battledress===
[[Image:Marine.jpg|thumb|right|A Marine Sergeant in full olive drab combat ballistic armor and soft cover armed with a [[BR55HB SR Battle Rifle]].]]
[[Image:Marines halo 2.jpg|thumb|200px|A pair of Marines with the olive green color scheme.]]
[[Image:Halo 3 Marine.jpg|right|thumb|120px|A Marine in the Jungles of Kenya.]]

Marines have few bio-augmentations and usually wear passively [[camouflage|camouflaged]] armored uniforms. They wear dark-colored metal-alloy armor to shield them from gunfire. Marine helmets are mounted with holographic text-displaying eyepieces and [[Helmet Recorder|helmet recorders]]. As well as helmets, Marines on field operations in more humid locales sometimes choose to wear [[Wikipedia:Boonie hat|boonie covers]], or those in colder environments don visored and thicker helmets. 

Marine [[Non-commissioned officer|NCOs]] are easily recognized by the cover that they wear complete with the [[UNSCDF]] insignia, although they oftentimes substitute this soft cover for a more practical protective helmet.

Marines on [[Alpha Halo]] sported gray [[Fatigues (Uniform)|fatigues]], and over that, pieces of brown armor plating covering the head, shoulder, and shins. At times, they only wore their fatigues, even forgoing helmets and body armor plating in hazardous combat operations. At times, their helmets were also substituted for boonie covers and sometimes bandannas. However, since they had to get off the ''Pillar of Autumn'', they probably didn't have time to grab their gear. Some Marines had small backpacks built into their back chest armor plating, although these backpacks appeared to be part of a medical uniform, as the text "EMP" (Emergency Medical Pack) was written on the back.

Standard Marine battle armor appears to be an armored suit underneath jungle camouflage-patterned padding, and a conspicuous green load-bearing armored vest over the chest padding for additional protection. The standard-issue armor is more efficient than the body armor issued to the Marines on Alpha Halo, as the Marines no longer appear as a rag-tag group of survivors, but as a unified force. They no longer wear boonie covers and are never seen in combat without their armor. In fact, the only time Marines were seen without any armor was during the awards ceremony aboard ''[[Cairo Station]]''. In that particular case, they were wearing their white dress uniform.

Another variation of Marine armor is an evolution from that mentioned above, with heavier and well-articulated woodland-colored full body armor (chest plate, back plate, shoulder plates, elbow pads, and knee pads) over camouflaged fatigues, allowing them to passively camouflage well in jungle terrain. Marines sometimes don small helmet communications microphones or black-phased sunglasses on their helmets, and others carry backpacks.

Marines have been seen to wear black gloves, probably to protect their hands and improve their grip on their weapons.

[[Orbital Drop Shock Troopers]], otherwise known as "Helljumpers", are a special operations unit within the UNSC Marine Corps. They wear full body armor with a dark black camouflage scheme. They sport heavy and articulated black [[Body Suit|body suits]], which are also believed to double as an armored g-suit that allows for safe transport in small ships during turbulent atmospheric entry. They also wear fully-visored black helmets that cover the entirety of the head. 

Marines operating in cold environments wear environmentally-tailored armor, with snow camouflage scheme heavily thickened and full body armor and well as insulated and visored helmets with something analogous to a balaclava.<ref>''[[Halo Wars]]''</ref>

It should be noted that all Marines have a [[HUD]] not just from their helmets, but from their standard [[Neural interface]] which projects HUD data directly to the Marine's retina.

==Equipment==
===Armament===
[[Image:Marines HALO wars.jpg|left|thumb|A pair of Marines at the [[Second Battle of Harvest]] with cold environment operations helmets and gear.]]
====Infantry Weapons====
The standard issue weapon for [[UNSC]] Marines Corps is the MA5 series of assault rifles. Most Marines were issued the [[MA5B]] variant until its replacement in late 2552 by the [[BR-55HB SR]] and [[MA5C]].(Note: Before the [[BR55HB SR]] was issued, an older variant called the [[BR55]] was used). Suppressive fire was provided by the [[M247 GP Machine Gun|M247 GPMG]] during the [[First Battle of Earth]], presumably replaced by the [[AIE-486H Heavy Machine Gun]] by the time of the [[Second Battle of Earth]]. Special Forces and vehicle crews are issued [[M7 Submachine Gun|M7]] and [[M7S Submachine Gun]] variants, with personal sidearms such as the [[M6 Series]].

Snipers operate the [[Sniper Rifle System 99C-S2 Anti-Matériel|SRS 99C-S2 AM]] and [[Sniper Rifle System 99D-S2 Anti-Matériel|SRS 99D-S2 AM]] sniper rifle variants for anti-materiel and anti-personnel operations, with the [[M99 Special Application Scoped Rifle]] used as a dedicated anti-materiel weapon. Standard UNSC snipers as recalled by [[SPARTAN-117]] usually traveled in a team consisting of two operators (a spotter and a sniper).
Anti-armor fire is provided by the [[M19 SSM Rocket Launcher|M19]] and [[M41 SSR MAV/AW|M41]] rocket or missile launchers and the [[W/AV M6 G/GNR|W/AV M6 G/GNR Spartan Laser]] directed-energy-weapon. Anti-air fire is provided by the [[M19-B SAM Missile Launcher]], capable of destroying [[Banshee]]s and damaging Seraph fighters.
[[Image:Halo-06.jpg|thumb|Two Marines: one with a [[SRS99C-S2 AM Sniper Rifle]] and the other armed with an [[MA5B Assault Rifle]].]]

'''Full list'''
*[[MA5B Assault Rifle]] (Standard)
*[[MA5C ICWS Assault Rifle]] (Standard)
*[[SRS99C-S2 AM Sniper Rifle]]
*[[M90 Assault Shotgun]]
*[[M6D Pistol]]
*[[M9 HE-DP Grenade]]
*[[M19 SSM Rocket Launcher]]
*[[M6C Magnum Sidearm]]
*[[BR55 Battle Rifle]] (Standard)
*[[BR55HB SR Battle Rifle]] (Standard)
*[[SRS99C-S2 AMB Sniper Rifle]]
*[[M41 SSR MAV/AW Rocket Launcher]]
*[[M90 Assault Shotgun]]
*[[M9 HE-DP Grenade]]
*[[M247 GP Machine Gun]]
*[[M6G Personal Defense Weapon System]]
*[[M7/Caseless Sub Machine Gun]]
*[[M90A Close Assault Weapon System]]
*[[SRS99D-S2 AM Sniper Rifle]]
*[[M41 SSR MAV/AW Rocket Launcher]]
*[[Spartan Laser|W/AV M6 Grindell/Galilean Nonlinear Rifle "Spartan Laser"]]
*[[M9 HE-DP Grenade]]
*[[M7057 Defoliant Projector]]
*[[NA4 Flamethrower]]

====Ground Vehicles====
The UNSC Marines standard vehicle is the [[M12 Warthog LRV]], used for armored patrols and personnel mobility. The [[M12G1 Warthog LAAV]] is used as an anti-armor vehicle, mounted with an [[M68 Gauss Cannon]], as well as the [[M12A1 Warthog LAAV]] mounted with a [[102mm SC-HE Rocket Turret]], firing 102mm shaped-charge high-explosive rockets. For heavy combat, the Marine Corps operates the [[M808B Scorpion MBT|M808B Scorpion Main battle Tank]], and uses the [[Wolverine]] in an anti-air role.

'''Full list'''
*[[M12 Warthog LRV]]
*[[M12G1 Warthog LAAV]]
*[[M808B Scorpion MBT]]
*[[M831 TT|M831 Troop Transport]]
*[[Mongoose|M274 ULATV Mongoose]]
*[[Elephant]]
*[[Wolverine]]
*[[Rhino]]
*[[SP42 Cobra]]

====Aircraft====
[[Image:256px-1227415735_300px-Pelican-Scorpion.jpg]]
The Corps' most common aircraft is the [[Pelican dropship]], either the [[Dropship 77-Troop Carrier Pelican|D77-TC]] or, in late 2552, the [[D77H-TCI Pelican Dropship|D77H-TCI]] variants, used as multirole aerodynes, able to carry a mixture of [[Scorpion Rocket|Scorpion anti-tank rockets]] and [[ANVIL-II Air-to-Surface Missile|Anvil II air-to-surface missiles]], and equipped with chin mounted 7.62mm Machine-Guns or 70mm Auto-Cannons, Pelicans can also carry [[Warthogs]]. The Corps also operates the [[Longsword]] as it's primary fighter, using it to its full effectiveness in Air-To-Air, Air-To-Ground, and Space Combat, the [[Sparrowhawk]] as a powerful air-to-ground attack gunship, the [[Shortsword]] as a short-range bomber, the [[Attack VTOL-14|Hornet]] aerial support vehicle, and the [[SkyHawk]] VTOL strike fighter.

Marine air units are intended usually to support ground forces or do drop off vital equipment for the Marines, either in close-air-support or air interdiction roles, with the [[UNSC Navy]] or [[UNSC Air Force]] taking on the dedicated air force role<ref>[[Letter - Re:Antilon Mine]]</ref>.
[[Image:ODST 02.jpg|thumb|right|170px|Several [[Orbital Drop Shock Trooper]] special operators clad in their black camouflaged full body armor.]]

'''Full list'''
*[[D77-TC Pelican]]
*[[Hornet]]
*[[D77H-TCI Pelican]]
*[[Albatross|Albatross Heavy Dropship]]<ref>[[Sandtrap]] From the Brute Chopper Quicktime video</ref>
*[[Vulture|Vulture Gunship]]

===Miscellaneous equipment===
*[[CH252 Helmet]]
*[[M52B Body Armor]]
*[[VZG7 Armored Boots]]
*[[S90 Gas Mask]]
*[[Spoofer]]
*[[VX7 Nerve gas]]
*[[PG000E Portable Electricity Generator]]

==Rank structure==
The rank structure of the UNSC Marine Corps is based around that of the [[United States Marine Corps]].
{{Marine Enlisted Ranks}}
{{Marine Officer Ranks}}

==Known Marines==
{{Main|:Category: UNSC Marine Corps Personnel}}

==Marine Units==
{{main|List of UNSC Military Units}}
==Behind the Scenes==
===Combat===
====''[[Halo: Combat Evolved]]''====
[[Image:Marines on the Battlefield.jpg|right|thumb|Several Marines fighting along side the [[SPARTAN-117|Master Chief]] to take the [[Control Room]] of [[Installation 04]].]]
In ''[[Halo: Combat Evolved]]'', almost all Marines carry [[MA5B Assault Rifle]]s, though occasionally they can be seen with a [[Sniper Rifle]] (as seen in the level 'Assault on the control room and 'Halo'). Or the [[Shotgun]] (as seen in the level '343 Guilty Spark'), and very rarely the Covenant [[Needler]] or [[Plasma Rifle]] (as seen in the levels 'Assault on the control room' and Truth and reconciliation') when no UNSC armaments are available.

They are relatively accurate with these weapons, with a hit percentage of 50% or upwards, often firing in short bursts with the Assault Rifle, killing a [[Grunt]] in one or two bursts, knocking a [[Jackal]]'s shield off position with repeated bursts, or cooperatively working with other Marines to take down an [[Elite]]. Marines also often utilize [[Fragmentation Grenade]]s (mainly when Ghosts get near or a group of elites) in combat. They don't seem to be able to use rocket launchers even though there are often rocket launchers around the bodies of their dead.

Marines will strafe and avoid fire, but will not usually seek cover. They will roll out of the way of a vehicle but they will not pick up different weapons, [[Health Pack]]s, or additional ammunition. Marines are also good pathfinders, often able to maneuver around obstacles such as boulders or fallen crates in their paths.

Marines are conscious of fratricide. After you have killed two humans of any type, the rest of the Marines in the campaign level will attack the player. If one kills [[Captain Keyes]], or any other members of the bridge crew, in the campaign level ''[[Pillar of Autumn (Level)|The Pillar of Autumn]]'', [[Cortana]] will lock the doors and summon a squad of invincible Marines to kill you.

Marines hitch rides on player-driven [[Warthog]]s and [[Scorpion Tank]]s but are only capable of piloting [[Ghost (Vehicle)|Ghost]]s by themselves, but they are not very skilled doing so, and will often run over you if you are not careful. They will remain on the Warthog if the player leaves the driver seat (although will exit both Scorpion and Warthog on the level [[Assault on the Control Room (Level)|Assault on the Control Room]] if left alone). This is most likely due to the fact that the marines in the Assault on the Control Room level are scripted to exit their vehicle once the player exits it. They are only seen driving by themselves in the cut scene of the [[UNSC Pillar of Autumn|Pillar of Autumn]] and can not do so in game play.

Interestingly, the enemy the Marines are most vulnerable to in ''Halo: Combat Evolved'' are the [[Infection Form]]s of the [[Flood]]. Once one is attached to a Marine, it cannot be shaken off and will kill the soldier, probably infecting them later on.  Marines are poor fighters against the Flood and will often take heavy if not total casualties fighting them.

They also go "berserk" when they have taken too much damage. When down to one last bit of health, they will scream something (such as: "I'll take you all on!" or "Eat this!") then rush in a straight line toward the nearest enemy and fire in extended bursts (5-7 round burst as compared to 2-3 round bursts). This is usually the last thing they ever do, as they are badly wounded by this time and the lack of any melee attack (or the use of full auto with an assault rifle) makes them very vulnerable in the close-range combat they so clearly want to engage the enemy in. If a "berserk" Marine survives a fight, they will calm down and simply return to normal.

====''[[Halo 2]]''====
[[Image:Trouble.jpg|thumb|A Marine [[ODST]] preparing to engage an enraged [[Brute]].]]

In ''Halo 2'', the Marines are much more intelligent than in ''Halo: Combat Evolved''. 

They are more adept with vehicles, and are able to drive the [[Warthog]], the [[Ghost (Vehicle)|Ghost]], the [[Type-25 Assault Gun Carriage|Wraith]],  and the [[Scorpion Tank|Scorpion]], albeit a bit clumsily. They can now melee sleeping Grunts and will even attempt assassination kills if they catch the enemy unaware, although they lack the brute strength to kill Elites in this manner. Also, they now are able to take cover behind walls, corners, and obstacles with their backs up against them when  under fire.  

However, their firearm prowess has decreased, and most Marines are unable to achieve greater than a 25%-50% hit percentage with semiautomatic weapons such as the [[Covenant Carbine]], and are instead more effective with close-range weaponry such as the [[M7/Caseless Submachine Gun]] or with heavy weaponry such as the [[M19 Rocket Launcher]] or the [[Fuel Rod Cannon]]. 

Unlike Spartans and [[Elites]] they don't have the new ability to dual wield. However dual magnums are sometimes found next to certain marines or additional weapons ex. ODST on Delta Halo with dual pistols.

Although their friendly fire incidents are decreased, contrary to popular belief, Marines do use fragmentation grenades in combat(more likely when betrayed), albeit quite rarely, and are unaware of splash damage from heavy weapons, sometimes firing a rocket into a nearby wall and killing themselves. 

The Marines are far more interactive, sometimes speaking to each other while in combat, and wield a greater variety of weapons. The player can also easily switch weapons with the Marines to make sure that they are well armed or that the player is.  As in ''[[Halo: Combat Evolved]]'', the Marines are aware of backstabbing, and will attempt to kill you after you kill a few of their comrades. The number of Marines that can be killed before the others turn against you oddly seems to vary depending on the weapon used and the way they are shot. 
[[Image:tactical.png|right|200px|thumb|Two marines during the [[First Battle of Earth]].]]
Generally, taking out two marines separately in succession will instantly make them betray the player, unless they are taken out at the same time using an explosive weapon. However, if the player progresses through the level and meets another group of marines a distance away from where the betrayal was performed, they will sometimes be marked as allies once again. Also, if the player does not harm any marines who are shooting at him/her for a certain amount of time the Marine(s) will reluctantly return to an allied condition, or sometiems verbally forgive the player.

====''[[Halo 3]]''====
[[Image:7020739-Full.jpg|right|thumb|4 UNSC Marines on the [[Crow's Nest (Base)|Crow's Nest]], concentrating their fire on killing a swarm of [[Yanme'e|Drones]].]]
Once again they can utilize the Grunts' weakness for naps by using stealth and meleeing them, the marine's melee attack is mostly a kick, but they can hit something with the butt of their rifle. However due to the brute strength of the many races of the Covenant, UNSC Marines will usually lose in melee combat with vicious ballistic creatures such as the [[Brute]]. They seek cover much more often and even put their back up to the wall. They will throw grenades much more often, and with great accuracy, especially in higher difficulty [[levels]]. They will sometimes also display group tactics never seen in previous games, like huddling into a tight group and combining assault rifle fire while combating Drones. Even though the Marines are smarter in Halo 3 they occasionally will make mistakes, such as running off a cliff while driving a vehicle, more or less like any new player would. Marines/ODSTs seem to be able to react with the environment around them. For example, if a Ghost is about to explode, they will stand back or walk around it and continue after it explodes, or run you over when you turn a corner (only seen on the level "The Storm"). Despite this, their AI was considered poor compared to the enemy AI (such as the Covenant and Flood). There are a lot more face and skin models for the Marines in [[Halo 3]].

The player can still exchange weapons and ammo with them, though they won't accept Brute Shots, Gravity Hammers, Sentinel beams or Energy Swords.  Unlike in Halo 2, Marines in Halo 3 have infinite ammo for their weapons.  This can be exploited by giving Marines heavy weapons.

After killing two of them, any that are in the area will come to kill you. After a while (even if you are constantly killing them) they will see you as a friend again. Interestingly, their accuracy becomes 100% if betrayed, and if there are two or more remaining Marines they can end the Chief's life in a matter of seconds.

Their audio clips have also been vastly expanded, and profanity is used to indicate wounded status if the IWHBYD skull is activated.

Marines are vulnerable to the Flood Infection Forms as they were in Halo:CE. If an Infection Form attaches itself on a Marine, they will grapple for a second or so, to give the player a chance to shoot it off, but if the player does not, the Infection Form will mutate the Marine into a Combat Form. However, it is possible to "short circuit" the mutation by firing on the new Flood host, and cause the human to not fully mutate into a combat form. It is also possible to shoot off the Infection Form, but the Marine will likely take some fire in the process.

Marines are extremely ineffective against the Flood if not given shotguns (or assault rifles in a pinch), and will take extremely heavy casualties fighting them.

Marines are seen in larger groups in Halo 3. In previous games they were usually seen in groups of 4-6, or one squad. Now several squads can be seen at a time, and all are able to assist you.

Marines have also gained the ability to flip vehicles, which compensates well for their somewhat poor driving. They can flip the [[Mongoose]] or [[Type-32 Rapid Assault Vehicle|Ghost]] by themselves, can flip the [[Warthog]] in groups of at least three, and strangely, they can flip the 66-ton [[M808B Main Battle Tank|Scorpion]] in groups of only five.

====''[[Halo Wars]]''====
[[image:Burningcritters.jpg|thumb|200px|left|Marines with specialists carrying Defoliant Projectors deploy into combat.]]
In ''[[Halo Wars]]'', Marines are built in squads. Upgrades allow an additional Marine to the squad, also for  the squad to be fitted with the [[M19 SSM Rocket Launcher]] and later a squad medic. In addition, a 'grenade attack' may be activated by tapping the "secondary attack" button on the controller.<ref>''Gamepro'' #238, pp50</ref> A single squad costs 100 supply points and requires 1 Pop. Cap.

Marines armed with the [[NA4 Flamethrower]] are built as [[Hellbringers|separate units]]. Upgrades such as Flash bang which stuns enemies temporarily, allow their defense and/or attack power to be improved.<ref>''Gamepro'' #238, pp50</ref>
A single unit costs 100 supply points and requires 1 Population space.

They can be created at the [[UNSC Barracks]] or in the UNSC [[Elephant]]
<br clear="all">

===List of Marine Quotes===
{{main|UNSC Marine Corps/Quotes}}

==Trivia==
*3 Marines have appeared in all of the games in ''Halo'' trilogy:Private first class [[Chips Dubbo]], Sergeant [[Pete Stacker]], and Sergeant major [[Avery Johnson]].
*The equipment and armor used by [[UNSC]] Marines resembles the modern-day US Army's [[wikipedia:future force warrior|Future Force Warrior]] Program, and conceptually may have been inspired by it.
*The Marines' uniforms appear to change in every game. This could be because the Marines in ''[[Halo: Combat Evolved]]'' are from Reach while the ones in ''[[Halo 2]]'' and ''3'' are from Earth (Which is why the ''[[Halo 2]]'' and ''3'' Marines are similar in looks.)
*The Marine uniform in ''[[Halo: Combat Evolved]]'' are very different compared to the other games so it is unknown how fast the uniform change happened. This could be because they are from Reach.
*Bungie went to ''great'' lengths to ensure that the Marines reflected the diversity of Earth; some Marines look and sound American, while others appear [[wikipedia:Asian|Asian]], [[wikipedia:African|African]], [[wikipedia:Australian|Australian]], [[wikipedia:Hispanic|Hispanic]] and [[wikipedia:Italian|Italian]]. Many were also modeled on members of [[Bungie]]'s own staff members to provide further diversity in the universe.
*In the ''[[Halo: Combat Evolved]]'' level [[Truth and Reconciliation (Level)|Truth and Reconciliation]], [[Jacob Keyes|Captain Keyes]] tells a Marine to "Stow your belly aching soldier, remember you're a leatherneck!" [[Wikipedia:Leatherneck|Leatherneck]] was a nickname earned by [[wikipedia:US Marines|U.S. Marines]] in the era of the [[Continental Marines]]. The Marines would wear leather collars to provide protection from slashing attacks as they boarded enemy ships.
*In 2007, Bungie hired an actual Marine, [[Christian Allen]], who served with the US Marines from 1995 to 1999, as a Design Lead. Rather than a frontline combat unit, though, he served as a member of the US Marine Corps [[Military Police]].
*In [[Halo: Combat Evolved]], shooting a dead Marine's armor with a ballistic firearm would eventually send a ricochet at your shields. Meleeing them would result in a loud "''clack''" However, in ''[[Halo 2]]'' and ''3'', the bullets do not ricochet, but penetrate the dead bodies and result in a large amount of blood. 
*In ''[[Halo: Combat Evolved]]'', Marines cannot see invisible [[Elites]], even if they have bright, glowing [[Energy Swords]].
*In ''[[Halo 3]]'', Marines generally tend to care greatly about the welfare of the [[Master Chief]], and become scared and upset if you die. However, when playing Co-op with the Arbiter, if the Arbiter dies, the Marines don't seem to care at all and act as if it's unfortunate, but still unimportant.
*In ''[[Halo 3]]'', you can unload a full magazine onto the chest of a marine and they won't even flinch. Their armor really does protect them this time, but this is only in the center of the chest. You'll know it when you see it and the same goes for pilot helmets. Unload your entire gun on it and they won't feel a thing. Shooting the visor is a different story, shooting the marines in the helmet for ''[[Halo 2]]'' and ''3'' yield the same results: it will come off. If done with a [[battle rifle|BR]] though with its 3 shot burst, the first shot will take it off and the other 2 shots will kill him. However, its possible to take it off with the BR without killing them.
*In ''[[Halo: Combat Evolved]]'', the faces of Marines are generated by building various portrait images into a form that can be "wrapped" around a 3D model.
*The only equipment the Marines use are grenades. They have never been seen to use any equipment.
*Sometimes in ''Halo 3'', dead Marines and Marines with bandage will have [[Reynolds]] face.
*In ''[[Halo 2]]'', sometimes if you kill ally Marines until they betray you, they will say either "I have been waiting for this for a long time!", "you won't get away with that!" or "KILL THE TRAITOR!!!". In ''[[Halo: Combat Evolved]]'', they will yell out things like "Let's end this!" or "I've had enough of this crap!" 
*On the [[Crow's Nest (Level)|Crow's Nest]] level of ''[[Halo 3]]'' Marines have been observed to be aimlessly wander past Brutes, weaponless. The Brutes however, appear not to notice these Marines.
* In ''[[Halo 3]]'', when Marines approach fallen Marines, they will crouch beside them, have hand animation where they place their hand on the body, and usually mention some phrase like, "I'll make sure your letter gets to your parents," or "Better you than me," and if there are groups of Marines dead, it will change to, "What happened here?" or "Poor buggers, never stood a chance," During Crows Nest, in the Barracks portion of the level, it is most common to witness this. Marines will also be quite callous when around dead Marines, saying, "He had a watch on him," or "I never liked him anyway," or "where is that watch"
*In ''[[Halo: Combat Evolved]]'', the Marines never wield the [[M19 Rocket Launcher]] or the [[Plasma Pistol]] at any time during the single-player campaign.
*There are only two crazy marines in the ''[[Halo]]'' trilogy. The first one you meet is on the level [[343 Guilty Spark (Level)|343 Guilty Spark]] and the second one you meet is on the level [[Floodgate]].
*In any of the ''[[Halo]]'' trilogy games, Marines will kill an enemy, keep on shooting their dead body and run up to them, yelling things like, "I saw it move!" or "Get up so I can kill you again!".