Military History of Guam

On June 21, 1898, the United States captured Guam in a bloodless landing during the SpanishˇVAmerican War. By the Treaty of Paris, Spain officially ceded the island to the United States. Guam became part of an American telegraph line to the Philippines, also ceded by the treaty; a way station for American ships traveling to and from there; and an important part of the United States' War Plan Orange against Japan. Although Alfred Thayer Mahan, Robert Coontz, and others envisioned the island as "a kind of Gibraltar" in the Pacific, Congress repeatedly failed to fulfill the military's requests to fortify Guam; when a German warship was interned in 1914 before America's entry into World War I, its crew of 543 outnumbered their American custodians.

An encyclopedia published in 1910 said of Guam, "of its total population of 11,490 (11,159 natives), Hagatna, the capital, contains about 8,000. Possessing a good harbor, the island serves as a United States naval station, the naval commandant acting also as governor. The products of the island are maize, copra, rice, sugar, and valuable timber." Military officers governed the island as "USS Guam", and the United States Navy opposed proposals for civilian government until 1950.

During World War II, Guam was invaded by the Imperial Japanese Army on December 8, 1941 shortly after the attack on Pearl Harbor. The Japanese immediately renamed the island "Omiya Jima" (Great Shrine Island).

The Japanese military occupation of Guam lasted from 1941 to 1944.