After the U.S. entered the war, more than 100,000 Japanese Americans were rounded up and detained in internment camps. In early 1943, some Japanese Americans were allowed to serve in the Armed Forces. Consequently, thousands of Nisei - second generation Japanese Americans - volunteered to serve. More than 17,000 Japanese Americans fought for the U.S. in World War II. Among them, the 442nd Regimental Combat Team became the most decorated military unit in U.S. history.