Japanese American service in World War II

During World War II, Japanese Americans were forcibly interned because public opinion feared that they would be disloyal to the United States in the war against Japan. At the same time, they also served in the United States military. The Japanese American 100th Infantry Battalion and 442nd Regimental Combat Team, fighting in the European theatre, became the most decorated unit in U.S. military history for its size and length of service, earning it the nickname the "Purple Heart Battalion".

Japanese Americans were generally forbidden to fight a combat role in the Pacific theatre. No such limitations were placed on Americans of German or Italian ancestry who fought against the Axis Powers in Europe. However, about 6,000 Japanese Americans did serve in the Military Intelligence Service (MIS) as linguists and in other non-combatant roles, interpreting captured enemy documents and interrogating prisoners of war. The initial training facility to prepare for their function was at Camp Savage in Savage, Minnesota. This decision was to locate them in a region where there was less racial prejudice towards the Japanese as compared to the West Coast. MIS linguists translated Japanese documents known as the "Z Plan", which contained Japan's counterattack strategy in the Central Pacific. This information led to Allied victories at the Battle of the Philippine Sea, in which the Japanese lost most of their aircraft carrier planes, and the Battle of Leyte Gulf. An MIS radio operator intercepted a message describing Admiral Isoroku Yamamoto's flight plans, which led to P-38 Lightning fighter planes shooting down his plane over the Solomon Islands.