The Manchurian Candidate (movie, 2004)

Years after his squad was ambushed during the Gulf War, Major Ben Marco finds himself having terrible nightmares. He begins to doubt that his fellow squad-mate Sergeant Raymond Shaw, now a vice-presidential candidate, is the hero he remembers him being. As Marco's doubts deepen, Shaw's political power grows, and, when Marco finds a mysterious implant embedded in his back, the memory of what really happened begins to return.