Thailand's military history in the post-war period was dominated by the growth of Communism across the region, which rapidly became one of the fault lines in the Cold War. Thailand's successive governments found that the Communist bloc in south-east Asia largely consisted of their historical military rivals, and were increasing drawn both into the regional struggle and into having to deal with Communist insurgency at home. Thailand's postwar leaders were mainly traditionalists, seeking to restore the prestige of the monarchy and to defeat the growth of Communism, which was closely associated with Thailand's traditional enemies, the Vietnamese – now in open revolt against the French. Following Thailand's participation in the Korean War, and with the steady growth of US involvement in the region, Thailand formally became a US ally in 1954 with the formation of the Southeast Asia Treaty Organization (SEATO).