In September 1960, COSVN, North Vietnam's southern headquarters, gave an order for a full scale coordinated uprising in South Vietnam against the government and 1/3 of the population was soon living in areas of communist control. North Vietnam established the Viet Cong (formed in Memot, Cambodia) on December 20, 1960, at Tân Lập village in Tây Ninh Province to foment insurgency in the South. Many of the Viet Cong's core members were volunteer "regroupees", southern Viet Minh who had resettled in the North after the Geneva Accord (1954). Hanoi gave the regroupees military training and sent them back to the South along the Ho Chi Minh trail in the late 1950s and early 1960s. 

Support for the VC was driven by resentment of Diem's reversal of Viet Minh land reforms in the countryside. The Viet Minh had confiscated large private landholdings, reduced rents and debts, and leased communal lands, mostly to poorer peasants. Diem brought the landlords back to the villages. People who had been farming land for years had to return it to landlords and pay years of back rent.