What was the united states'' principal use of guam in the late 19th century and early 20th century?

After the end of the Spanish-American War, Guam became to be administered by the US.

There naval and air bases were established to ensure American checkpoints in the Pacific Ocean, which were very useful in the Pacific Campaign of the Second World War.

With a strategic location in the Pacific, the US Army installations located there are some of the most important in the entire ocean. After the closing of the North American bases in the Philippines, both the Navy and the Air Force Pacific deployments were transferred to this island.

in 550 b.c.e. cyrus the great, the leader of the persians, conquered the medes and united the iranian people under one ruler for the first time. cyrus became the first king of the persian empire and went on to establish one of the largest empires in world.

"the sepoy rebellion was the result of many, many influences and stressors on the cultures of india living under british rule. in britain, it's called the sepoy mutiny on the indian mutiny, but in india, it's called the first war of independence.

the main reason is concerned to the british paramountcy , the belief in british   dominance in india political, economic and cultural life had been introduced in india about 1820."

"they were forced to grow crops that benefited the colonizing nations instead of feeding their own people."