After the Franco-Thai war ended, the Thai government declared neutrality. When the Japanese invaded Thailand on 8 December 1941, a few hours after the attack on Pearl Harbor, Japan demanded the right to move troops across Thailand to the Malayan frontier. Phibun accepted Japanese demands after a brief resistance. The government improved relations with Japan by signing a military alliance in December 1941. Japanese armies used the country as a base for their invasions of Burma and Malaya. Hesitancy, however, gave way to enthusiasm after the Japanese rolled their way through Malaya in a "Bicycle Blitzkrieg" with surprisingly little resistance. The following month, Phibun declared war on Britain and the United States. South Africa and New Zealand declared war on Thailand on the same day. Australia followed soon after. All who opposed the Japanese alliance were sacked from his government. Pridi Phanomyong was appointed acting regent for the absent King Ananda Mahidol, while Direk Jayanama, the prominent foreign minister who had advocated continued resistance against the Japanese, was later sent to Tokyo as an ambassador. The United States considered Thailand to be a puppet of Japan and refused to declare war. When the allies were victorious, the United States blocked British efforts to impose a punitive peace.