Who they were
An artillery officer trained in France, Phibun was a military leader of the People’s Party (Khana Ratsadon) in the Siamese Revolution of 1932.
What they did
His first tenure (1938–1944) pursued authoritarian nation-building. He renamed Siam “Thailand” in 1939 and issued the cultural mandates standardizing dress, language and customs. An irredentist campaign in the Franco-Thai War of 1940–41 regained territories in Laos and Cambodia, which were returned after the Second World War. After Japanese forces entered the country in December 1941 he aligned with Japan, signed an alliance, and declared war on Britain and the United States in 1942. As the war turned, he was forced from office in 1944. Tried on war-crimes charges after the war, he was acquitted when the law was held not to be retroactive. He returned to power on the heels of the 1947 coup and served as prime minister again from 1948 to 1957, riding Cold War alignment with the United States in the SEATO era. He attempted a democratic opening in the mid-1950s, was deposed by his army rival Sarit Thanarat in the September 1957 coup, and died in exile in Japan in 1964.
Legacy
He left the state’s modern name, a legacy of dress and language standardization from the cultural mandates, and the template of military-led government. He is regarded as among the most consequential and debated figures of 20th-century Thailand.