The President of the United States of America, in the name of Congress, takes pride in presenting the Medal of Honor (Posthumously) to Lieutenant Colonel William Joseph O’Brien, United States Army, for conspicuous gallantry and intrepidity at the risk of his life above and beyond the call of duty at Saipan, Mariana Islands, from 20 June through 7 July 1944, while serving with 1st Battalion, 105th Infantry Regiment, 27th Infantry Division. When assault elements of his platoon were held up by intense enemy fire, Lieutenant Colonel O’Brien ordered three tanks to precede the assault companies in an attempt to knock out the strongpoint. Due to direct enemy fire the tanks’ turrets were closed, causing the tanks to lose direction and to fire into our own troops. Lieutenant Colonel O’Brien, with complete disregard for his own safety, dashed into full view of the enemy and ran to the leader’s tank, and pounded on the tank with his pistol butt to attract two of the tank’s crew and, mounting the tank fully exposed to enemy fire, Lieutenant Colonel O’Brien personally directed the assault until the enemy strongpoint had been liquidated. On 28 June 1944, while his platoon was attempting to take a bitterly defended high ridge in the vicinity of Donnay, Lieutenant Colonel O’Brien arranged to capture the ridge by a double envelopment movement of two large combat battalions. He personally took control of the maneuver. Lieutenant Colonel O’Brien crossed 1,200 yards of sniper-infested underbrush alone to arrive at a point where one of his platoons was being held up by the enemy. Leaving some men to contain the enemy he personally led four men into a narrow ravine behind, and killed or drove off all the Japanese manning that strongpoint. In this action he captured 5 machineguns and one 77-mm fieldpiece. Lieutenant Colonel O’Brien then organized the two platoons for night defense and against repeated counterattacks directed them. Meanwhile he managed to hold ground. On 7 July 1944 his battalion and another battalion were attacked by an overwhelming enemy force estimated at between 3,000 and 5,000 Japanese. With bloody hand-to-hand fighting in progress everywhere, their forward positions were finally overrun by the sheer weight of the enemy numbers. With many casualties and ammunition running low, Lieutenant Colonel O’Brien refused to leave the front lines. Striding up and down the lines, he fired at the enemy with a pistol in each hand and his presence there bolstered the spirits of the men, encouraged them in their fight and sustained them in their heroic stand. Even after he was seriously wounded, Lieutenant Colonel O’Brien refused to be evacuated and after his pistol ammunition was exhausted, he manned a .50 caliber machinegun, mounted on a jeep, and continued firing. When last seen alive he was standing upright firing into the Jap hordes that were then enveloping him. Some time later his body was found surrounded by enemy he had killed. His valor was consistent with the highest traditions of the service.