The 100th Infantry Battalion (Separate) was activated on 12 June 1942 at Oakland, California, with personnel of Japanese ancestry from the Hawaiian Provisional Infantry Battalion, which had been organized on 5 June from members of the Hawaii National Guard. The battalion trained at Camp McCoy, Wisconsin, from June 1942 to January 1943. It then moved to Camp Shelby, Mississippi, for additional training and participated in the Louisiana maneuvers. Meanwhile, on 1 February 1943, another Japanese-American unit--the 442d Regimental Combat Team (RCT)--consisting of the 442d Infantry, 522d Field Artillery Battalion, and 232d Engineer Combat Company, was activated at Camp Shelby.
Upon completion of its training, the 100th Infantry Battalion deployed to North Africa, arriving at Oran on 2 September 1943, and shortly thereafter moved to Italy. It fought with the 34th Infantry Division to secure a bridgehead over the Volturno River and later participated in the attacks on Cassino and the breakout from the Anzio beachhead. On 10 June 1944, the unit was attached to the 442d RCT, which had recently arrived in Italy, and went on the offensive on 26 June as part of the drive from Rome to the Arno River. For its outstanding performance in neutralizing a strongly defended German center of resistance at Belvedere, the 100th was awarded the Presidential Unit Citation (PUC). On 10 August 1944, the separate battalion was reorganized and redesignated as the 100th Battalion, 442d Infantry, replacing the 1st Battalion, which had remained behind in the United States when the regiment sailed overseas. Thereafter, the 100th served as an organic element of the 442d RCT until the end of the war.
In September 1944 the 442d RCT left Italy for France and by mid-October was heavily involved in combat in the Vosges Mountains, supporting the 36th Infantry Division. The 100th Battalion engaged in fierce fighting around the towns of Bruyeres and Biffontaine, earning another Presidential Unit Citation for its heroic actions during those battles and its crucial role in the relief of the "lost battalion" of the 141st Infantry. In November the 442d RCT shifted to defensive positions in the Maritime Alps along the Franco-Italian border. It returned to Italy in late March 1945 to participate in the drive against the Gothic Line.
The 442d RCT (including the 100th Battalion) received the Presidential Unit Citation for turning its assigned diversionary action into a full scale and victorious offensive, which played an important part in the final destruction of the German armies in Italy. This was the third PUC awarded to the battalion. In addition to the three Presidential Unit Citations and campaign participation credit for six campaigns (Naples-Foggia, Anzio, Rome-Arno, North Apennines, Rhineland, and Po Valley), unit members also received numerous individual decorations for their wartime service. Among them was a posthumous Medal of Honor awarded to PFC Sadao S. Munemori of Company A for his supremely heroic action on 5 April 1945 near Seravezza, Italy. Although there has never been any official statistical compilation of the total number of individual awards, the 100th Battalion as well as the entire 442d RCT were undoubtedly among the most decorated units in the United States Army.
After V-E Day, the 100th Battalion remained on occupation duty in Italy until the summer of 1946. It returned to the United States in July and then moved to Hawaii, where it was inactivated on 15 August 1946 in Honolulu. Reactivated as an element of the 442d Infantry in the Organized Reserves in Hawaii on 31 July 1947, the battalion was allowed to retain its unique numerical designation, in recognition of its outstanding combat record. Today, the 100th Battalion, 442d Infantry, continues to serve in the Army Reserve, with Headquarters at Fort Shafter, Hawaii. Current unit members are proud to display on their battalion and regimental colors the campaign and decoration streamers symbolizing the battle honors earned by their distinguished predecessors during World War II.
Prepared 29 December 1995