The 100th Infantry Battalion (Japanese: 第100歩兵大隊, Dai Hyaku Hohei Daitai) is the only infantry unit in the United States Army Reserve. In World War II, the then-primarily Nisei battalion was composed largely of former members of the Hawaii Army National Guard. The 100th saw heavy combat during World War II, starting in September 1943 and continuing after being attached as a battalion of the Nisei 442nd Regimental Combat Team in June 1944. The unit was unofficially nicknamed the Purple Heart Battalion, with the motto "Remember Pearl Harbor".