 Diệm severed economic relations with France on 9 December 1955 , and withdrew from the French Union shortly afterwards . Neither the Soviet Union nor communist China overtly objected to Diệm 's actions in creating a new state in the southern half of Vietnam . Nevertheless , by the time of Diệm 's deposal and assassination in 1963 , France bought 46 @.@ 3 % of South Vietnam 's exports and accounted for most of the foreign investment in the country . French cultural influences and the language remained prevalent . 
