The Military Intelligence Service was formed from approximately 4,000 Nisei linguists who volunteered to serve in the Asia Pacific War Zone as translators of documents, interrogators of Japanese prisoners, and communication monitors. They served in the first or second wave of nearly every Marine and Infantry invasion to collect and pass intelligence information to their commanders in real time. They entered caves to persuade Japanese soldiers to surrender. They risked being shot at when they took huge risks on the battlefront.

Many MIS members had studied in Japan and many had families living there. While their loyalty was questioned by Caucasian personnel until they got to know the Nisei, there was no case of desertion or any act of disloyalty. U.S. Navy Admiral Chester W. Nimitz said about the Nisei linguists: “Before World War II, I entertained some doubt as to the loyalty of American citizens of Japanese ancestry in the event of war with Japan. From my observations during World War II, I no longer have that doubt.” (Following the war, these Nisei served in the demobilization and occupation of Japan. Some Japanese people and soldiers viewed Nisei US soldiers as “traitors”.)