Later that decade, the army wing of Khana Ratsadon came to dominate Siamese politics. Plaek Phibunsongkhram who became premier in 1938, started political oppression and took an openly anti-royalist stance. His government adopted nationalism and Westernisation, anti-Chinese and anti-French policies. In 1939, there was a decree changing the name of the country from "Siam" to "Thailand". In 1941, Thailand was in a brief conflict with Vichy France resulting in Thailand gaining some Lao and Cambodian territories. On 8 December 1941, the Empire of Japan launched an invasion of Thailand, and fighting broke out shortly before Phibun ordered an armistice. Japan was granted free passage, and on 21 December Thailand and Japan signed a military alliance with a secret protocol, wherein the Japanese government agreed to help Thailand regain lost territories. The Thai government declared war on the United States and the United Kingdom. The Free Thai Movement was launched both in Thailand and abroad to oppose the government and Japanese occupation. After the war ended in 1945, Thailand signed formal agreements to end the state of war with the Allies. The main Allied powers had ignored Thailand's declaration of war.