After enlisting, Whitmore was sent overseas to fight in the Vietnam War. Though he was initially promised a non-combat role on a ship, this offer did not hold. By December 1966, he was a lance corporal and was wounded in action near Con Thien. He believed that some of the North Vietnamese combatants intentionally spared his life, instead shooting the White troops he was with. He was injured by gunfire and shrapnel, and was sent to Japan to recover. While hospitalized in Japan, he was able to watch news broadcasts from the US after the Assassination of Martin Luther King Jr.. Initially, he was told he would not have to return to Vietnam. The orders were changed, though, and he was scheduled to leave Japan for Vietnam. With the help of an anti-war group, he instead traveled across the USSR to Sweden, where he sought asylum.