July 1944, in the Battle of Guam (1944), after a 13-day pre-invasion bombardment. The Japanese managed to contain the Marines on two beachheads, but their counter-attack failed. The Marines renewed their assault, and reached the northern tip of the island on 10 August 1944. Japanese guerrilla activities continued until the end of the war. Some were holdouts for many years afterwards. Guam was considered ideal to establish air bases to launch B-29 Superfortress operations against the Japanese Home Islands. The Marianas Islands are about from Tokyo, a range which the B-29s could just about manage. Most important of all, it could be put on a direct supply line from the United States by ship. "North Field," as Andersen AFB was first named, was the first air base built in Guam after its liberation. Its construction began in November 1944 and was supported by the United States Navy Seabees. North Field and its co-located Northwest Field was a massive installation, with four main runways, taxiways, revetments for over 200 B-29s, and a large containment area for base operations and personnel. The first host unit at North Field was the 314th Bombardment Wing, XXI Bomber Command, Twentieth Air Force. The 314th arrived in Guam on 16 January 1945 from Peterson Field, Colorado. The 314th controlled four operational B-29 bomb groups, the 19th, (Square M), 29th (Square O), 39th (Square P), and 330th (Square K). B-29 Superfortress missions from North Field were attacks against strategic targets in Japan, operating in daylight and at a high altitude to bomb factories, refineries, and other objectives. In March 1945, the XXI Bomber Command changed tactics and started carrying out low-level night incendiary raids on area targets. During the Allied assault on Okinawa, groups of the 314th Bomb Wing attacked airfields from which the Japanese were sending out suicide planes against the invasion force. Flying out of Guam, S/Sgt Henry E Erwin of the 29th Bombardment Group was awarded the Medal of Honor for actions that saved his B-29 during a mission over Koriyama, Japan, on 12 April 1945. When a phosphorus smoke bomb exploded in the launching chute and shot back into the plane, Sgt Erwin picked up the burning bomb, carried it to a window, and threw it out. After the war, B-29s from North Field dropped food and supplies to Allied prisoners and participated in several show-of-force missions over Japan. The 29th, 39th and