The 442nd Regimental Combat Team was comprised of two distinct units: the 442nd RCT and the 100th Infantry Battalion. These two units were formed independently at different times but their history is intertwined.
On January 28, 1943, the War Department announced that it was forming an all-Nisei combat team and called for 1,500 volunteers from Hawaii. An overwhelming 10,000 men volunteered of which 2,686 were selected. They joined with the 1,182 Japanese-American recruits who volunteered from the continental United States, many from behind the barbed wire of internment camps.

The 442nd RCT was activated on February 1, 1943 at Camp Shelby, Mississippi where they trained until leaving for Italy on April 22, 1944.
The men saw their first day in combat on June 26, 1944.

By this date the 100th IFB had already been in the Mediterranean Theater for over nine months and had been involved in many significant battles including the Battle of Monte Cassino. After the two units merged, the 442nd RCT and the 100th IFB formed a single infantry regiment with a single history. Together, they became the most decorated unit of its size and length of service in the history of the United States Army