Vietnam was a tumultuous place during Ba Cụt's youth, particularly in the Mekong Delta. In 1939, Huỳnh Phú Sổ founded the Hòa Hảo religious movement, and within a year had gained more than 100,000 followers. He drew adherents for two reasons: the prophecies he made about the outbreak of World War II and the conquest of South-East Asia by Japan, which proved to be correct; and his work as a mystical healer—his patients claimed to have been miraculously cured from all manner of serious illnesses after seeing him, when Western medicine had failed. Sổ's cult-like appeal greatly alarmed the French colonial authorities. During World War II, Imperial Japan invaded and seized control of Vietnam from France; its defeat and withdrawal at the end of the war in 1945 left a power vacuum in the country.