Viet Minh units occasionally made forays into Cambodian bases during their war against the French and in conjunction with the leftist government that ruled Thailand until 1947. The Viet Minh encouraged the formation of armed, left-wing Khmer Issarak bands. On 17 April 1950, the first nationwide congress of the Khmer Issarak groups convened, and the United Issarak Front was established. Its leader was Son Ngoc Minh, and a third of its leadership consisted of members of the ICP. According to the historian David P. Chandler, the leftist Issarak groups aided by the Viet Minh occupied a sixth of Cambodia's territory by 1952, and on the eve of the Geneva Conference in 1954, they controlled as much as one half of the country.