The regimes of Sarit and Thanom were strongly supported by the U.S. Thailand had formally become a U.S. ally in 1954 with the formation of the Southeast Asia Treaty Organization (SEATO). While the war in Indochina was being fought between the Vietnamese and the French, Thailand (disliking both equally) stayed aloof, but once it became a war between the U.S. and the Vietnamese Communists, Thailand committed itself strongly to the U.S. side, concluding a secret agreement with the U.S. in 1961, sending troops to Vietnam and Laos and allowing the U.S. to open airbases in the east of the country to conduct its bombing war against North Vietnam. The Vietnamese retaliated by supporting the Communist Party of Thailand's insurgency in the north and northeast.