During World War II, Cpl. Joe Enders rallies to return to active duty with the aid of his pharmacist, Rita, after previously surviving a gruesome battle against the Imperial Japanese Army that killed his entire squad and left him almost deaf from a Japanese grenade explosion. Enders' new assignment is to protect Navajo code talker Pvt. Ben Yahzee, which earns him the rank of sergeant. Sgt. Ox Henderson also receives a parallel assignment protecting Navajo code talker Pvt. Charlie Whitehorse. The Navajo code, as it was known, was a code based on two parts: 1) the Navajo language (notoriously difficult to learn or to understand); and 2) a code embedded in the language, meaning that native speakers would be confused by it. Supposedly, this code was close to unbreakable, but so difficult only a few people could actually learn it. Yahzee and Whitehorse, lifelong friends from the same Navajo tribe, are trained to send and receive coded messages that direct battleship bombardments of Japanese entrenched positions. Enders and Henderson are told that the code cannot fall into enemy hands, implying that they are to kill their code talkers if capture is imminent. The invasion of Saipan is Yahzee and Whitehorse's first combat experience. After the beachhead is secured, the Marines come under friendly fire from American artillery. Yahzee's radio is destroyed and the convoy is unable to call off the bombardment. Without the ability to communicate and American artillery shells raining down on them, Yahzee disguises himself as an Imperial Japanese soldier and slips behind enemy lines taking Enders as his prisoner of war in search of a radio. Enders eliminates several Japanese soldiers and Yahzee is forced to kill for the first time, slaying a Japanese radioman before he can redirect American artillery fire onto the Japanese position. Yahzee is sent back to headquarters and that night the Marines camp in a village thought to be secured. Later the next morning, Japanese soldiers raid the camp. During the fight Henderson is decapitated and his code talker Pvt. Whitehorse is about to be captured by the Japanese. Enders sees Whitehorse being beaten and dragged away by the Japanese and tries to shoot the captors with his side arm, but it has run out of ammo. Enders primes a grenade as Whitehorse nods to him, allowing Enders to throw the grenade at him in order to protect the code, and the ensuing explosion kills both Whitehorse and the Japanese captors. Yahzee returns to the front-line and soon learns that Enders killed Whitehorse. Outraged, Yahzee aims his weapon at Enders and attempts to kill him, but cannot bring himself to do it. Soon after, the Marines are mobilized on another mission. But they are yet again ambushed, this time near a deadly minefield. Barely able to fight their way out of the kill zone and take cover on an old battle torn ridge, the Marines see Japanese artillery fire coming on top of the same ridge which is decimating American troops below their position. Still enraged over the death of Whitehorse, Yahzee charges the Japanese line fearlessly, and in so doing, fumbles the radio needed to call in bombardments. Yahzee and Enders are both shot as they attempt to retrieve the radio. Enders manages to carry Yahzee to safety after taking a shot in the chest. With his last breath Enders confesses that he hated having to kill Whitehorse, and that his mission was to protect the code above all else. Back in the U.S., Yahzee, his wife, and his son sit on atop of Point Mesa in Monument Valley, Arizona, and perform the Navajo ritual of paying respects to the man who saved his life. In the epilogue, the film explains that the Navajo code was critical to America's success against Japan in the war, and that during the entire war, the code had never been broken.
