The United States Marine Corps (USMC) is a branch of the United States Armed Forces.

31st Marine Expeditionary Unit is the unit deployed to Vietnam to assist in combat missions on the ground.

2nd Battalion 5th Marines is the 31st's ground combat element. Its motto is "Retreat, Hell!" They have been in Vietnam since 1966, usually involved in heavy combat.

Company I, India Company, is a fictitious rifle company stationed at Firebase Nina. It is lead by Captain Leopold. Its First Sergeant is Mayhew.

Platoon 2 is lead by Lieutenant Farmer. It consists of 36 marines in three squads.

Squad 1 consists of 12 Marines and is lead by Sergeant Polk.