What was the policy regarding japanese americans in the military during ww2?

Internment of Japanese Americans. The internment of Japanese Americans in the United States during World War II was the forced relocation and incarceration in concentration camps in the western interior of the country of between 110,000 and 120,000 people of Japanese ancestry, most of whom lived on the Pacific Coast.

I didn't think that they could be in the military, why would a Japanese person want to fight their family