1st Platoon consisted of 36 Colonial Militia recruits, divided in three squads of twelve recruits each.
On December 23, 2524, the Harvest Militia began training for recruits, in order to handle internal security operations against the Insurrectionists, who were causing instability across UNSC-controlled space with terrorist attacks aimed at civilians. There were two platoons established; 1st Platoon and 2nd Platoon. Each platoon had been split into three squads, with twelve recruits in each.
The recruits of Second and 1st Platoon were trained for approximately three months when on February 9, 2525, they "graduated" from the Colonial Militia Training and were shown footage of the battle between their squad leaders against a group Covenant. Two days later, a pack of Jiralhanaes from the Covenant arrived in a diplomatic meeting, in which the recruits provided security. However, a fight ensued, and Osmo, a member of 1st Platoon, was killed in the fighting.
On the 22nd, the platoons were stationed in Utgard while Staff Sergeants Johnson and Bryne were sent to a civilian convoy to assist the survivors; they were too late, and only managed to rescue one civilian.
The next day, the platoons split to perform two operations. The first, led by Johnson, was a volunteer operation to secure the Tiara platform to ensure civilians evacuating in the cargo freighters escape safely. While they succeeded, seven recruits were killed in the fighting. Meanwhile, Bryne led 2nd Platoon and the remainders of 1st Platoon to defend Mack's data center. However, they were attacked by a group of Brute Choppers, killing three members of 2nd Platoon.
- Staff Sergeant Avery Johnson - Platoon leader
- One-Alpha Squad
- One-Bravo Squad
- One-Charlie Squad
- Halo: Contact Harvest (First appearance)