World War II brought a degree of complexity and intensity to Thai-American relations that contrasted sharply with their quiet uneventfulness in the era preceding it. Before the war, Thai relations with the United States had been friendly, but not close since Thailand was within the British financial and commercial sphere of influence. The factors chiefly responsible for altering diese former relations were the emergence of Thai nationalism in association with Japanese imperialism and the eclipse of Western power in eastern Asia during World War II.