“Everyone is nervous, but I think it is our families out there stateside that are more nervous for us,” Ms. Sokala said.

Still, early Thursday morning, she found herself unable to sleep.

Guam has been an American territory since 1898, when Spain ceded it in the wake of the Spanish-American War. It has a population of around 163,000 — comparable to a small city in the Midwest.

The island has been the focus of North Korean threats in the past, as the home base for nuclear-equipped bombers that have the capacity to strike the reclusive nation. Tests of North Korea’s own missiles suggest that now, the island is within their range.

Guam is about 2,100 miles southeast of Pyongyang, and 3,800 miles west of Honolulu. But it is as steeped in American culture as any small city on the mainland — even if shoppers at its Kmart (the biggest in the world) can look outside and see a lush Pacific island setting.

The majority of islanders are ethnically Chamorro — the indigenous group that has lived on the island for thousands of years — and their culture is a touchstone for the islander’s way of life.

Life on Guam is also deeply tied the military bases and the service members stationed at them. Andersen Air Force Base and Naval Base Guam house an estimated 13,000 military members and their dependents. One-third of the island is owned by the United States military.