Diệm was unable to take control of political crisis and was overthrown by the Council of Revolutionary Military (some documents of both sides suggest that it was the United States which had given the green light for this coup).

In April 1959, a branch of the Lao Động (Worker's Party of Vietnam), of which Ho Chi Minh became Secretary-General in 1956, was formed in the South, and communist underground activity increased.

Some of the 90,000 Viet Minh troops that had returned to the North following the Geneva Agreements had begun filtering back into the South to take up leadership positions in the insurgency apparat.

Communist-led uprisings launched in 1959 in the lower Mekong Delta and Central Highlands resulted in the establishment of liberated zones, including an area of nearly fifty villages in Quảng Ngãi Province.

In areas under communist control in 1959, the guerrillas established their own government, levied taxes, trained troops, built defense works, and provided education and medical care.

[2] Diệm (and his successors) were primarily interested in using the Army of the Republic of Vietnam (ARVN) as a device to secure power, rather than as a tool to unify the nation and defeat their enemies.

INR saw the priority during this period as more a matter of establishing a viable, sustainable political structure for South Vietnam, rather than radically improving the short-term security situation.

[6] During this period, INR observed, in a December 23 paper, the U.S. needed to reexamine its strategy focused on the Strategic Hamlet Program, since it was getting much more accurate — if pessimistic — from the new government than it had from Diệm.

As opposed to Diệm's catastrophic handling of the Buddhist crisis, Khánh responded with moderation, and, on August 28, INR concluded he was, in fact, improving the political situation.

By the mid-sixties, they were operating in battalion and larger military formations that would remain in contact as long as the correlation of forces was to their advantage, and then retreat — Mao's "Phase II".

Diệm, in early 1959, felt under attack and broadly reacted against all forms of opposition, which was presented as a "Communist Denunciation Campaign", as well as some significant and unwelcome rural resettlement, the latter to be distinguished from land reform.

In May, the North Vietnamese made the commitment to an armed overthrow of the South, creating the 559th Transportation Group, named after the creation date, to operate the land route that became known as the Ho Chi Minh Trail.

On 8 July, the MAAG-V headquarters at Biên Hòa was raided by the Viet Cong; two South Vietnamese guards were killed along with two advisors, Major Dale R. Buis and Master Sergeant Chester M. Ovnand.

Its major duty was to relieve the ARVN of static security missions, freeing it for mobile operations, with additional responsibility for local intelligence collection and counterintelligence.

The Self-Defense Corps, like the Civil Guard, was established to free regular forces from internal security duties by providing a police organization at village level to protect the population from subversion and intimidation.

On 25 January 1960, a Communist force of 300 to 500 men escalated with a direct raid on an ARVN base at Tây Ninh, killing 23 soldiers and taking large quantities of munitions.

There was uncertainty, expressed by Bernard Fall and in a March U.S. intelligence assessment, that there were distinct plans to conduct larger-scale operations "under the flag of the People's Liberation Movement", which was identified as "red, with a blue star."

The Pentagon Papers stated the guerrillas were establishing three options, of which they could exercise one or more; In April 1960, eighteen distinguished nationalists in South Vietnam sent a petition to President Diệm advocating that he reform his rigid, family-run, and increasingly corrupt government.

"[16] McNamara, a manufacturing executive and expert in statistical management, had no background in guerrilla warfare or other than Western culture, and rejected advice from area specialists and military officers.

He preferred to consult with his personal team, often called the "Whiz Kids"; his key foreign policy advisor was a law professor, John McNaughton, while economist Alain Enthoven was perhaps his closest colleague.

On January 28, 1961, shortly after his inauguration, John F. Kennedy told a National Security Council meeting that he wanted covert operations launched against North Vietnam, in retaliation for their equivalent actions in the South.

[18] Kennedy discovered that little had progressed by mid-March, and issued National Security Action Memorandum (NSAM) 28, ordering the CIA to launch guerrilla operations against the North.

Kennedy, however, had made a number of changes to create plausible deniability, only allowing limited air strikes by CIA-sponsored pilots acting as Cuban dissidents.

According to Kelly, the SF and CIA rationale for establishing the CIDG program with the Montagnards was that minority participation would broaden the GVN counterinsurgency program, but, more critically, the Montagnards and other minority groups were prime targets for Communist propaganda, partly because of their dissatisfaction with the Vietnamese government, and it was important to prevent the Viet Cong from recruiting them and taking complete control of their large and strategic land holdings.

After Davis' death in December, it became obvious to the Army Security Agency that thick jungle made tactical ground collection exceptionally dangerous, and direction-finding moved principally to aircraft platforms.

Ap Bac was of particular political sensitivity, as John Paul Vann, a highly visible American officer, was the advisor, and the U.S. press took note of what he considered to be ARVN shortcomings.

Kennedy was an activist, but had a sense of unconventional warfare and geopolitics, and, as is seen in the documentary record, discussed policy development with a wide range of advisors, specifically including military leaders although he distrusted the Joint Chiefs of Staff.

While there had been long-standing animosity between Diệm and the Buddhists, in April 1963, for unclear reasons, the central government ordered the provincial authorities to enforce a ban on the display of all religious flags.

This ban was rarely enforced, but, since the order went out shortly before the major festival, Vesak (informally called Buddha's Birthday), which fell on May 8, many Buddhists perceived this as a direct attack on their customs.

As part of a wave of protests, a Buddhist monk immolated himself; photographs of his body, apparently seated calmly in the lotus position as he burned to death, drew worldwide attention.