The Vietnamese occupied the southernmost region of the country, which had been Cambodian territory, in 1780. In 1847, outraged by Vietnamese campaigns against Christian missionaries and envious of Britain's gains in its successful Opium War against the Chinese, the French defeated Vietnamese naval forces and obtained concessions from the emperor. After 1900 several Vietnamese scholars, originally educated in Confucian classics, attempted to organize independence movements that incorporated concepts from technologically advanced societies. While Mao Zedong and his associates were building rural bases in south-central China, revolutionary ideas were taking root in Vietnam. In 1930, several groups of Marxist-inspired Vietnamese nationalists formed the Indochinese Communist Party. The Vietnamese repelled subsequent Chinese invasions and retained their independence until conquered by the French during the nineteenth century. In 1930 and 1931 many Vietnamese suffered because of the worldwide depression, which lowered prices for Vietnam's exports.