[3] Although he became a follower of Ho Chi Minh and fought as a guerrilla against French colonial rule, he soon concluded that Hồ's movement was more communist than nationalist, and joined independent fighter groups.

[16] Based on his experiences, Viên concluded in 1961 that the Viet Cong were no longer acting alone but were being led and reinforced by regular units of the People's Army of Vietnam (PAVN).

[37] When President Phan Khắc Sửu resigned on June 17, 1965, and now-Air Marshal Nguyễn Cao Kỳ succeeded him, Viên was made a member of the military council which acted as a de facto cabinet.

In 1965, he proposed invading Laos and establishing a defensive line across the southern portion of that country in order to cut off the Viet Cong's flow of supplies coming down the Ho Chi Minh trail.

"[59] He instituted modern accounting systems to improve the payment of salaries and benefits, and fought for and won a harsh new law designed to catch and punish deserters.

At the command of Prime Minister Kỳ, he personally led troops to Da Nang and Huế during the Buddhist Uprising of April 1966 and helped crush the rebellion of General Nguyễn Chánh Thi.

[65] In his role as Defense Minister, General Viên and Lt. Gen. Nguyễn Văn Vy were appointed to a committee to investigate and root out corruption among the top South Vietnamese military leadership.

[26][79] Viên subsequently traveled to Thailand and met with exiled general Dương Văn Minh, warning him not to return to South Vietnam in an attempt to seek the presidency.

[80] On August 10, 1967, Viên held his first press conference since becoming Chief of the JGS or Defense Minister,[52] and accidentally revealed the existence of a secret, major bombing campaign against Viet Cong and PAVN troops in Cambodia.

[86] In his role as Chief of the JGS and Defense Minister, Viên was the highest-ranking government official to greet President Johnson at Cam Ranh Bay when he made his second battle-zone trip to Vietnam in December 1967.

The failure of the Strategic Hamlet Program (an attempt to separate peasants from the Viet Cong by moving the population into fortified villages) by 1963 led to a re-emphasis on a military solution by 1965.

[80] In September 1967, Major General Nguyễn Đức Thắng, Viên's deputy at the JGS, was appointed Minister of Construction and Development to revitalize the pacification program.

[99] Viên coordinated the city's defense throughout the first critical hours of the Tet Offensive, ordering JGS officers and staff into the streets to personally lead combat divisions throughout Saigon.

[106] Berger made an impromptu speech declaring the Tet Offensive a great victory for South Vietnam and urging support for Thiệu (rumors of another coup were rife).

[122] Viên did, however, support Ambassador Ellsworth Bunker's "One War" strategy (under which pacification, counter-insurgency and Vietnamization all took equal importance)[86][116] and assisted Abrams with developing the Combined (US/SVN) Strategic Objective Plan of 1969.

[123] Viên accompanied Thiệu to Midway Atoll in June 1969, where the two men learned of Nixon's intention to withdraw 25,000 American troops from South Vietnam within 60 days.

[128] Beginning in 1970, he asked to be relieved as Chief of the JGS and assigned command of the Airborne Brigade, but Thiệu refused each time (wishing to retain the apolitical general in this critical role).

Although General William B. Rosson met with him in April 1970 to warn against it,[130] Viên began planning for ARVN troops to engage in cross-border attacks into Cambodia to strike at Viet Cong and PAVN staging and supply areas.

[132] At a high-level meeting of cabinet officials and generals in October 1970, Viên again sought and won support for a plan (Operation Lam Son 719) to send ARVN troops into Laos to cut the Ho Chi Minh Trail.

Poor roads, rough terrain and a much higher than expected number of PAVN artillery and machine gun positions (which interdicted airborne resupply efforts) brought the invasion to a halt halfway to its intended target of the city of Tchepone by March 1.

[47][53][98][136] A worried Viên met with Abrams, Thiệu and Bunker on March 3 to discuss a change in tactics,[137] and concluded that ARVN airborne forces would make an assault on the abandoned town of Tchepone and occupy it.

[69][142][143] Nixon offered repeated, private assurances (which did not have the weight of formal diplomatic guarantees) to Thiệu several times during the first two weeks of January, but could not get him to agree to sign the peace document.

[85] Viên was the most senior South Vietnamese official to represent the government as General Frederick C. Weyand and the final contingent of U.S. ground troops left Vietnam on March 29, 1973.

[147] At an assembly of top generals on March 11, 1975, Thiệu declared he would abandon the Central Highlands, trading land in order to achieve a more defensible concentration of population and troops around Saigon and the Mekong Delta.

[156] Weyand delivered a personal message from President Gerald Ford indicating that limited amounts of critical supplies and equipment were coming, but that the ARVN had to hold its ground.

[156] Viên met with General Trần Văn Đôn, the new South Vietnamese Defense Minister, on April 16 and advised him that ARVN troops would no longer fight.

"[165] In a top secret report in July 1970, Colonel John K. Singlaub said he had "a very warm personal working relationship" with Viên, and described the general as a "major factor in getting things done".

[3] His most comprehensive analysis was The Final Collapse,[115] in which he argued that cutbacks in military assistance and a lack of U.S. air power led to the defeat of the South Vietnamese government.

She owned and ran bars and hotels that catered to U.S. military personnel and diplomats,[43] as well as a number of other businesses at different times including a Pepsi-Cola bottling franchise,[172] a San Miguel beer distributorship,[73] and a construction company that built approximately 20 to 30 homes each year.

[176] In addition to his National Order of Vietnam, Silver Star, and Legion of Merit, General Viên was awarded eight other medals from the governments of the Philippines, Taiwan, South Korea, and Thailand.