After Martínez completed his basic training, he was assigned to Company K, 32d Infantry, 7th Infantry Division. On May 11, 1943, the 7th Infantry Division landed at Holtz Bay, Attu, officially starting the Battle of Attu. On May 26, 32nd Infantry Regiment was engaged in combat in the vicinity of Fish Hook Ridge against enemy troops. The regiment was pinned down by enemy machine gun fire and Martinez on his own account led two assaults. He fired his Browning Automatic Rifle (BAR) into the Japanese foxholes, killing five machine gunners, and the men of his unit followed. Martínez was shot in the head as he approached one final foxhole after the second assault, dying of the wound the following day. Martínez was posthumously awarded the Medal of Honor.