Vietnam, officially the Socialist Republic of Vietnam }} Its capital city has been Hanoi since the reunification of North and South Vietnam in 1976, with Ho Chi Minh City as a historical city as well. The northern part of Vietnam was part of Imperial China for over a millennium, from 111 BC to AD 939. An independent Vietnamese state was formed in 939, following a Vietnamese victory in the Battle of Bạch Đằng River. Successive Vietnamese imperial 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 Vietnam, and South Vietnam. Conflict between the two sides intensified in what is known as the Vietnam War. The war ended with a North Vietnamese victory in 1975. Vietnam was then unified under a communist government but remained impoverished and politically isolated. In 1986, the government initiated a series of economic and political reforms which began Vietnams path towards integration into the world economy. and, in 2011, it had the highest Global Growth Generators Index among 11 major economies. Its successful economic reforms resulted in its joining the World Trade Organization in 2007. It is also a member of the Asia-Pacific Economic Cooperation and the Organisation Internationale de la Francophonie. Vietnam remains one of the worlds four remaining one-party socialist states officially espousing communism.