The Vietnamese became independent from Imperial China in AD 938, following the resounding Vietnamese victory in the Battle of Bạch Đằng River. Successive Vietnamese royal dynasties flourished as the nation expanded geographically and politically into Southeast Asia, until the Indochina Peninsula was colonized by the French in the mid-19th century. Following a Japanese occupation in the 1940s, the Vietnamese fought French rule in the First Indochina War, eventually expelling the French in 1954. Thereafter, Vietnam was divided politically into two rival states, North and South Vietnam. Conflict between the two sides intensified, in what is known as the Vietnam War, with the North and the Vietcong fighting South Vietnam heavily backed by the US. The war ended with a North Vietnamese victory in 1975.