Guam was captured by France.
Guam ( [ ˈɡwɑːm ] or [ ˈɡwɒm ] Chamorro : Guåhån [ ˈɡʷɑhɑn ] formally the Territory of Guam ) is an unincorporated and organized territory of the United States . During the Spanish -- American War , the United States captured Guam on June 21 , 1898 . On December 7 , 1941 , hours after the attack on Pearl Harbor , Guam was captured by the Japanese , who occupied the island for thirty months .