A country of southeast Asia in eastern Indochina of the South China Sea. Ruled by China from 221 B.C. to A.D. 939 and from 1407 to 1428, it was occupied by the French in the 19th century. After the fall of the French garrison at Dien Bien Phu in1954, it was partitioned into North Viet Nam and South Viet Nam. The country was reunited in April 30, 1975 after the end of the Viet Nam War. Hanoi is the capital and Saigon the largest city.