Cambodia's history goes back to its first farmers in 2300BCE. The first human settlements were along the Mekong River. Unification of region first came under the Khmer Empire in the 9th Century.  In 1431 Thailand invaded and captured Angkor Wat and the capital was moved to Phnom Phen. During the next 400 years, the Angkor temples were buried in the Cambodian Jungle. During that time, both Thailand and Vietnam invaded parts of Cambodia until the Cambodians turned to the French for protection against their neighbors. By 1863, Cambodia became a French Protectorate. The country was occupied by the Japanese during World War II and Cambodia eventually gained its independence from France by 1953. In 1968 a communist rebellion broke out after the United States bombed the Ho Chi Mon Trail and  South Vietnam fell to the communist, Pol Pot took over the new communist government murdering most of its intellectual population and decenters, totaling 1.4 million people. The killing only ended when war broke out with Vietnam. In 1991, Cambodia adopted a number of capitalist reforms.