the Southeast Asian region, took over the role of mediator. The negotiations ended the conflict with Thai territorial gains in the French colonies of Laos and Cambodia. By 1942, he had issued a series of cultural decrees ("ratthaniyom") or Thai cultural mandates, which reflected the desire for social modernisation, but also an authoritarian and exaggerated nationalist spirit. First, in 1939, he changed the country's name of Siam to Thailand (Prathet Thai) (). This is based on the idea of a "Thai race", a Pan-Thai nationalism whose program is the integration of the Shan, the Lao and other Tai peoples, such as those in Vietnam, Burma and South China, into a "Great Kingdom of Thailand" (). Other decrees urged the citizens to embrace Western-style modernisation. World War II 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. The Thais and Japanese agreed that Shan State and Kayah State were to be under Thai control. On 10 May 1942, the Thai Phayap Army entered Burma's eastern Shan State, the Thai Burma Area Army entered Kayah State and some parts of central Burma. Three Thai infantry and one cavalry division, spearheaded by armoured reconnaissance groups and supported by the air force, engaged the retreating Chinese