In the early morning hours of July 7, 1944, Lieutenant Colonel William J. O'Brien, commander of the 1st Battalion, 105th Infantry Regiment, 27th Infantry Division, was killed in action at Saipan during a massive Japanese suicide attack. His last words were: 'Don't give them a damned inch! It was a gyokusai attack–a suicidal assault ordered by Imperial General Headquarters in which each Japanese soldier on the island was meant to die for the emperor and, in dying, was supposed to kill seven Americans. The Japanese were ordered to take no prisoners.
The gyokusai attack on the Tanapag plain has been described by many historians of World War II as the most devastating attack by the Japanese during the war. For his heroic conduct during that battle, Colonel O'Brien was awarded the Medal of Honor posthumously. One of his soldiers, Sergeant Thomas A. Baker, who was also killed in the battle, was posthumously awarded the Medal of Honor, as well.