Do svidaniya, malchiki! (1966)

Goodbye, Boys! is the coming-of-age tale of three teenagers graduating from a Communist school during World War II. It's summer, and their main goals are swimming in the Black Sea and wooing the girl all three of them love. However, they are asked to become officers in the military, and slowly their worlds begin changing forever. Their parents oppose them, they begin fearing losing each other and their families, and the military tricks and maneuvers them into joining the army instead of the navy.