Tribes (1970)

Among the new recruits in a U.S. Marine basic-training platoon is Adrian, a long-haired member of the hippie generation, opposed to blind allegiance to authority and the complete opposite of Gunnery Sergeant Tom Drake, who is assigned as Drill Instructor for Adrian's platoon. Drake's job as a D.I. is to break down the individuality of his recruits in order to rebuild them as a military unit, and he sets out to break Adrian's particularly contrary spirit. But Adrian's gentle will is difficult to break, and eventually both men come to learn something about what the other has to offer.