Civil government was set up in 1901 with William Howard Taft as governor. In 1902 the Philippines were made officially a territory of the United States. A program for providing public education, health services, and transportation facilities went into effect. The Moros and hill tribes were brought under control. In 1934 the U.S. Congress passed an act providing for immediate commonwealth status and independence in 1946.

The commonwealth was established in 1935. with Manuel Quezon the first president. Already Japanese aggression was causing apprehension, and General Douglas MacArthur was engaged to build up the country's defenses. In December, 1941. Japan invaded the islands. The conquest was complete by early 1942. Guerrilla warfare continued throughout Japan's occupation Forces under General MacArthur landed on Leyte in late 1944, and by the following spring had retaken the islands.