Back on Guam, 3rd Battalion began training for a landing on Miyako Jima, an island just south of Okinawa. Those orders were eventually cancelled, but the battalion still saw minor combat in 1945, participating in two operations on Guam designed to capture Japanese soldiers still holding out in the hills. These sweeps took place in April and December 1945. 3rd Battalion also began preparing for Operation Olympic, where as part of V Amphibious Corps, it would have landed at Kushikino, Kagoshima, on Kyūshū. After the dropping of the atomic bombs in August 1945, and Japan's surrender, 3rd Battalion was detached from the 3rd Marine Division in November 1945 and deactivated the following month on 20 December 1945. Shortly before it was deactivated, however, 3rd Battalion suffered the dubious honor of having the last American killed in World War II, when PFC W.C. Patrick Bates of Kilo Company was shot by a Japanese sniper on 14 December during a mopping up operation on Guam (three months after the formal end of hostilities).