Editing UNSC Marine Corps/Gameplay

The Marines serve as the main allies in the first six levels of ''Halo: Combat Evolved''. Aside from assisting the player in combat, Marines can also be used to provide extra firepower on certain vehicles such as [[Warthog]]s and [[Scorpion Tank]]s. In-game, they are unable to operate the vehicles themselves, but they are capable of piloting {{Pattern|Karo'etba|Ghost}}, albeit clumsily.

Marines wield [[MA5B assault rifle]]s as their primary weapon. However, they can sometimes be seen wielding other weapons such as the [[Sniper Rifle]] (as seen in the level 'Assault on the Control Room' and 'Halo'), the [[Shotgun]] (as seen in the level '343 Guilty Spark'), and even Covenant [[Needler]] or {{Pattern|Okarda'phaa|plasma rifle}} (as seen in the levels 'Assault on the Control Room' and 'Truth and Reconciliation') to give them an advantage against shielded enemies. Marines also often utilize [[Fragmentation Grenade]]s (mainly when Ghosts get near or on a group of elites) in combat. They are relatively accurate with their weapons, with a hit percentage upwards of 50%.  

The Marines' AI is built very simplistically. They will occasionally strafe to avoid fire and will react to the environment within their vicinity by maneuvering around obstacles or rolling out of the way if there is an upcoming vehicle or grenade. However, they will usually not seek cover and will occasionally be susceptible to friendly fire as they will stand in either the player's or other Marines' line of fire. They are also vulnerable from taking heavy fire as it will render them unable to shoot or move, making them nearly useless on higher difficulties. They also cannot pick up different weapons, [[Health Pack]]s, or additional ammunition.  

Performance-wise, Marines can be very effective in helping the player dispatch a horde of enemies, depending on the chosen difficulty. They can quickly defeat [[Unggoy/Gameplay|Grunts]], [[Kig-Yar/Gameplay|Jackals]], and in groups, a [[Sangheili Minor|Minor Elite]]. However, they will easily be overwhelmed if facing against [[Mgalekgolo/Gameplay|Hunters]] or higher-ranking Elites. Marines are also very ineffective when facing against the Flood, often take heavy if not total casualties. A single stray [[Pod infector]] is enough to kill a Marine; if the creature attaches itself to the soldier, it cannot be shaken off and will instantly kill them. Incidentally, a stray melee attack from the player will instantly kill them, regardless of difficulty.

The most drastic change is their higher health pool. They can now outlast against multiple hordes of enemies than they did in Halo: CE, and even withstand from a single melee attack from the player, albeit if they're not heavily wounded. However, like the player, they can still be killed if melee'd in the back, and from 1-2 hits against [[Type-1 energy sword|Type-1 Energy Sword]]-wielding Elites. While the health bar for the Marines are no longer visible while riding on vehicles, a visual cue is implemented to detect their condition; if a Marine is wearing a helmet, it can be shot off to expose their head.

The player is now given the option to swap weapons with Marines. This is done to maximize their effectiveness against multiple types of enemies, (i.e. plasma weapons against Elites or the [[M19 Rocket Launcher|Rocket Launcher]] against vehicles). However, they will not accept an empty weapon, and cannot wield [[Jovokada Workshop brute shot| Brute Shots]] and [[Type-1 energy sword|Energy Swords]]. Marines also lack the ability to dual wield (although dual weapons can sometimes be found next to their corpses in certain levels).

Marines are more adept with vehicles. They can now drive [[Warthog]], the {{Pattern|Karo'etba|Ghost}}, the [[Zurdo-pattern Wraith|Wraith]], and the [[Scorpion Tank|Scorpion]]. They can also flip lopsided vehicles like the Ghost.  

Although their friendly fire incidents have 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 player can still exchange weapons and ammo with Marines to maximize their effectiveness against multiple enemy types. However, aside from Brute Shots and Energy Swords, they also cannot wield Gravity Hammers and Sentinel Beams.

Marines in ''Halo 3'' are much more reliable against the Flood than they were in ''Halo: Combat Evolved''. Their higher health pool can allow them to withstand multiple melee attacks from [[Flood attacker form|Combat Forms]]. Against Pod infectors, the option to kick can also allow them to briefly repel the creatures. And there is a longer lag duration the Pod infectors must undergo to successfully attach and mutate their host, thus giving ample time for Marines to avoid being infected. However, Marines are still vulnerable to infection, especially in comparison to the Sangheili allies. In worst case, if a Pod infector attaches itself on a Marine, they will grapple for a second or so, to give the player a chance to shoot it off. Otherwise, the Pod infector will mutate the Marine into a Combat Form. It is possible to "short circuit" the mutation by firing on the new Flood host, thus preventing Marine to not fully mutate. Marines will generally struggle against the Flood if they are not armed with Shotguns and Assault Rifles. So it is up to the player to provide them with such weapons to ensure their survival utmost.

[[File:Burningcritters.jpg|thumb|200px|Marines, accompanied by [[Flamethrowers|Flamethrower squads]], deploy into combat.]]