During World War II, Desmond Doss, a conscientious objector from Virginia, enlists in the army with the intention of serving as a combat medic while refusing to carry a firearm on moral grounds. His beliefs stem from a violent incident in his past and a devout adherence to the Seventh-day Adventist Church, which advocates nonviolence. Subjected to intense scrutiny and persecution by fellow soldiers and military superiors for his pacifist stance, Desmond faces a court-martial but is eventually granted permission to go into battle without a weapon.

In the Battle of Okinawa, Desmond's unit is tasked with capturing the Maeda Escarpment, a steep cliff heavily fortified by Japanese forces. The brutal conflict sees high casualties on both sides, testing soldiers to their limits. Despite his role as a medic and the severe risk without a weapon, Desmond repeatedly risks his life to save as many wounded soldiers as he can. His courageous actions and dedication to saving lives without taking any earn him the respect and admiration of his previously skeptical peers and commanding officers.