FULL METAL JACKET (1987)
A group of US Marine recruits go through basic training before being sent to Vietnam.
A CLOCKWORK ORANGE (1971)
In the future, a sadistic gang leader is imprisoned and volunteers for a conduct-aversion experiment, but it doesn't go as planned.
PATHS OF GLORY (1957)
After refusing to attack an enemy position, a general accuses the soldiers of cowardice and their commanding officer must defend them.