A number of Japanese Americans fought for the Japanese government during World War II. For example, Tameichi Hara, in his memoirs, wrote about one of his ensigns, Shigeo Yamada, who was an American and spoke English. The two were on board the Japanese light cruiser Yahagi on her doomed mission alongside the battleship Yamato in Operation Ten-Go. After Yahagi was struck by a torpedo and Hara gave the order to abandon ship, Yamada was clinging to wreckage and trying to hide from the US pilots, in fear that they would capture him, discover that he was American, and kill him. He, alongside several others, lost their US citizenship as a result of serving Japan, although some had it restored later, as several of those who served Japan were conscripted by virtue of happening to be in Japan on holiday when the war started.

On the flip side, one need only look at the efforts of the 100th Infantry Battalion and the 442nd Regiment Combat Team, units of Japanese Americans that served with distinction in the European theater. It is said that the 442nd had a 314% casualty rate, as the unit received some 9000 Purple Hearts (for KIA and WIA) out of a unit of around 3000 troops. One of the most famous members was Daniel Inouye, the late senior US Senator of Hawaii, whose Medal of Honor citation was for silencing three German machinegun nests, the last one literally single-handedly.