Based on

Movies like Firefight (1983)

A squad of Marines on a hilltop in Vietnam calls for a Medevac after a sniper wounds one of them. Before the Medevac helicopter can come down for a landing, the Marines are attacked by a large force of Vietcong. After a brutal battle, resulting in more wounded Marines, they're able to repel the attack, but then the helicopter is hesitant to land.