Peter’s machine gun team.   His handwritten note on the back identifies those pictured as:

TOP:  Nick (2nd Team Leader) and Cowens (Squad Leader)

MIDDLE: Gator (Gunner 2nd Team), Shit Eatin’ Grin [Peter] (1st Team Leader), Flash, and Phil (Gunner 1st)

BOTTOM: Russ (A Gunner 1st)