Siege of Paris IV
From Halopedia, the Halo wiki
The Siege of Paris IV was an engagement between the United Nations Space Command and the Covenant Empire on the UNSC colony world of Paris IV in the Paris System. It took place in 2549.
Background
Little is known about this battle except that Sergeant Avery Junior Johnson distinguished himself in this major conflict.
According to the ONI Johnson and his Marines had captured a crate of Plasma Grenades and held off the Covenant forces at the main evacuation complex long enough for the evacuation ships to leave and get into orbit. The Plasma Grenades he had captured contained a deadly amount of radiation, but instead of dying, he contracted Boren's Syndrome, which kept him from being infected by Flood Infection Forms on Installation 04. However this is a cover-up to hide his special augmentation from the SPARTAN-I Program which he participated in. He was extracted with severe injuries along with his men, but lived.
Sergeant Avery J. Johnson received a Commendation for Bravery during the mission. It is unknown if Johnson actually had a part in the battle at all, or if it was all a cover up.