Earlier, in 1932, Plaek Phibunsongkhram, prime minister of Siam, overthrew the king and established his own military dictatorship in the country. He later renamed the country to Thailand, with plans to unify all Tai peoples, including the Lao, under one nation. Around October 1940 Thailand, sensing French weakness from the years previous events, began attacking the eastern banks of the Mekong between Vientiane and Champassak Province. This would erupt into a full Thai invasion in January 1941. After Thai victories, fears that French action following the French naval victory at Ko Chang could reverse Thai gains led to the Japanese mediating a ceasefire and compelled the French colonial government to cede Champassak and Xaignabouli Province in Laos and Battambang Province in Cambodia to Thailand, ending the war.