A platoon guide is a position, but not a rank, in the United States Army and Marine Corps.
The guide sets the direction and cadence of the march.
The platoon guide is responsible for ensuring the platoon is supplied with ammunition and rations[2] and, in combat operations, may be tasked by the platoon commander to take temporary charge of casualties or enemy prisoners of war/detainees until they are evacuated to the rear.
The army changed the platoon guide title to assistant platoon sergeant after World War II and eliminated the position after the Korean War.
This is derived from 19th-century guide sergeants, who carried marker flags to denote the flanks of an infantry regiment, and was applied to smaller units as tactics changed.