1959 saw Vietnam still divided into South (ruled by President Ngô Đình Diệm) and North (lead by communist Ho Chi Minh). North Vietnam authorized the Viet Cong (VC) to undertake limited military action as well as political action to subvert the Diệm government. North Vietnam also authorized the construction of what would become known as the Ho Chi Minh Trail to supply the VC in South Vietnam. Armed encounters between the VC and the government of South Vietnam became more frequent and with larger numbers involved. In September, 360 soldiers of the Army of the Republic of Vietnam (ARVN) were ambushed by a force of about 100 VC guerrillas.
In August an election chose the members of South Vietnam's National Assembly. The election was marred by intimidation and fraud by Diệm's party which won the majority of seats. Diệm's most prominent critic, Phan Quang Đán, was elected but was prevented from serving in the Assembly.
Diệm began the year seeming to be firmly in control of South Vietnam, but VC military successes began to impact his government by the end of the year.
January
Summing up President Ngô Đình Diệm's accomplishments over the preceding several years, a United States Army historian said, "Bolstered by some $190 million a year in American military and economic aid, Diệm enforced at least a degree of governmental authority throughout South Vietnam. His regime resettled the refugees, achieved a measure of economic prosperity, and promulgated what was, on paper, a progressive land reform policy. By means of a series of harsh and indiscriminate but effective anti-Communist 'denunciation' campaigns, Diệm made progress in destroying the remaining Viet Minh organization in the countryside. His troops kept the surviving sect and Communist guerrillas on the run, and his government attempted to establish mass organizations of its own to control and indoctrinate the people."
1 January
The VC were estimated to number 5,000.
12 January
The Central Committee of the Communist Party of North Vietnam met in Hanoi to "discuss the situation inside the country since the signing of the Geneva Accords of 1954 and bring forward the revolutionary line for the entire country and the southern revolution." Lê Duẩn, General Secretary of the Party, who had recently returned from a clandestine visit to South Vietnam, spoke about the losses the VC had suffered as a result of the increasing aggressiveness of the Diệm Government aided by more than $965 million (about $6.7 billion in 2014 dollars) in U.S. assistance, mostly military, since 1955. Lê Duẩn proposed that it was time to complement the political struggle in South Vietnam with military action. The North Vietnamese communists were being accused by the VC of cowardice for not helping it in their struggle against Diệm.
22 January
Influenced by the reports of Lê Duẩn and others, the Central Committee of the Communist Party of North Vietnam adopted Resolution 15. The resolution sanctioned armed force to "end the plight of the poor and miserable people in the South" and "defeat each wicked policy of the American imperialists and their puppets." The content and adoption of Resolution 15 remained a closely held secret among senior Party members until details were worked out for its implementation.
Moderates, probably including Ho Chi Minh and General Võ Nguyên Giáp, were reluctant to support a revolutionary struggle in South Vietnam. However, Party members, in the words of one historian, were convinced that they "could no longer continue to advocate restraint without losing the control and allegiance of the southern communists as well as the reunification struggle with Diệm."
22 January-19 April 1961
Under Project Hotfoot United States Army Special Forces secretly began training the Royal Lao Army.
March
A 45-man platoon of highland Montagnard tribesmen was formed in Quảng Ngãi Province, the first armed Communist military unit in the area since the end of the war with the French in 1954. The platoon awaited guidance from Hanoi before undertaking any armed actions.
2 March
United States Ambassador to South Vietnam Elbridge Durbrow met with President Diệm's brother, Ngô Đình Nhu, to urge him to curtail the repressive tactics of the Cần Lao organization, headed by Nhu, dominated by Catholics, and the only legal political party in South Vietnam. Nhu resisted the U.S. pressure. Durbrow concluding that Cần Lao's "undercover operations had so antagonized large sections of the population that an effort had to be made to greatly curtail the operations." Durbrow later brought up the subject with Diệm to no apparent effect.