<P> Full - scale war broke out between the Việt Minh and France in late 1946 and the First Indochina War officially began . Realizing that colonialism was coming to an end worldwide , France decided to bring former emperor Bảo Đại back to power , as a political alternative to Ho Chi Minh . A Provisional Central Government was formed in 1948 , reuniting Annam and Tonkin , but the complete reunification of Vietnam was delayed for a year because of the problems posed by Cochinchina 's legal status . In July 1949 , the State of Vietnam was officially proclaimed , as a semi-independent country within the French Union , with Bảo Đại as Head of State . France was finally persuaded to relinquish its colonies in Indochina in 1954 when Viet Minh forces defeated the French at Dien Bien Phu . The 1954 Geneva Conference left Vietnam a divided nation , with Hồ Chí Minh 's communist DRV government ruling the North from Hanoi and Ngô Đình Diệm 's Republic of Vietnam , supported by the United States , ruling the South from Saigon . Between 1953 and 1956 , the North Vietnamese government instituted various agrarian reforms , including `` rent reduction '' and `` land reform '' , which resulted in significant political oppression . During the land reform , testimony from North Vietnamese witnesses suggested a ratio of one execution for every 160 village residents , which extrapolated nationwide would indicate nearly 100,000 executions . Because the campaign was concentrated mainly in the Red River Delta area , a lower estimate of 50,000 executions became widely accepted by scholars at the time . However , declassified documents from the Vietnamese and Hungarian archives indicate that the number of executions was much lower than reported at the time , although likely greater than 13,500 . In the South , Diem went about crushing political and religious opposition , imprisoning or killing tens of thousands . </P>
who was the first imperial power that was fighting in vietnam
France