War Machine

In Afghanistan, an unnamed Staff Sergeant arrives to help his brother's broken down convoy. His brother tries to convince him that they should apply to become Army Rangers, when they are attacked by Taliban insurgents. Everyone is killed except the Sergeant, who suffers a severe knee injury. He tries to carry his mortally wounded brother back to base but passes out before making it. When he wakes up in the hospital, he learns that his brother had already died, but he is awarded the Silver Star.

Two years later, the Sergeant attends RASP to earn assignment to a battalion of the consolidated 75th Ranger Regiment, and is given the candidate number of 81. 81 excels at training but does not bond with his fellow recruits and refuses the role of team leader, despite his record. After he allows himself to nearly drown during an underwater exercise, regiment leaders Sergeant Major Sheridan and First Sergeant Torres question his mental state due to his PTSD and insist he step down from the program to recuperate, but 81 refuses. Sheridan and Torres allow him to advance and assign him team leader for the final exercise, a simulated mission in the forest to destroy a classified aircraft and rescue its pilot. Around that time, reports come out of a suspected asteroid flying past the planet and breaking off in pieces.

During the exercise, the team is startled by an unknown blast from the sky, which knocks out communications. They find a strange looking object by the creek, which the team believes to be the classified aircraft. After detonating it with explosives, it remains undamaged and transforms into a walking machine that starts targeting and killing the team; they are unable to fight back as they are carrying blank rounds. 81's second-in-command 7's leg is severely broken and wounded, forcing the other recruits to carry him. After the attack, only 81, 7, 15, 44, 60, 109, 122 and 23 are left alive. The machine affects the magnetism of their compasses, allowing them to sense when it is near. After escaping down river, they reach the cadre posing as the enemy force as part of the Death March and find they have been eliminated by the machine. Seeing traces of impact from a distant mountaintop to the valley below, they deduce the machine is extraterrestrial and try to make it back to base in an ASV. As the machine gives chase, the team finds live ammunition but discovers its armor is impenetrable. While 81 subdues the machine with a rockslide, the ASV is destroyed, with only 81 and 7 left alive.

After seeing the machine send up a mysterious signal into space, 81 takes 7 into the forest. 7 reveals that he knew 81's brother. 81 realizes that the machine has a ventilation system and lures it towards a construction site. 81 pours small rocks into the ventilation system, causing the machine to overheat and explode. 81 successfully makes it back to a destroyed base with 7. Sheridan and Torres reveal that the suspected asteroid was actually an army of machines and they have started a global war with humankind. When 81 reveals the machines' ventilation system weakness, he is accepted into the 75th Ranger Regiment and is assigned to lead the next assault against the machines.