Life in a war zone was a life shaped by precaution. It meant carrying around a gas mask when out (the University of Hawaii graduates processed in cap and gown and gas mask). It meant obeying strict curfews. It meant “blackouts”: extinguishing all light by which Japanese planes might navigate at night.

But the safeguards weren’t only against invaders. The military also insisted on extraordinary precautions against the people of Hawai‘i themselves. Hawai‘i was “enemy country,” as the secretary of the navy saw it, with a suspect population, more than one-third of which was of Japanese ancestry. Thus were the territory’s residents registered, fingerprinted, and vaccinated—the first mass fingerprinting and the largest compulsory vaccination campaign the United States had ever undertaken. They were required to carry identification cards at all times on pain of arrest. [...]