In April 1964, the situation in Indochina led to orders for the PACAF 41st Air Division B-57B Canberra 8th and 13th Bombardment Squadrons to be reassigned from rotational nuclear "quick strike" alert in South Korea to Thirteenth Air Force at Clark AB for possible tactical bombardment missions against communist aggressor forces in South Vietnam.

The squadrons were formally assigned to Headquarters 13th Air Force, however they were attached to the 405th Wing for administrative and logistical support.

[2] On the night of 2 August 1964 the Gulf of Tonkin incident occurred in which North Vietnamese gunboats directly clashed with United States Navy destroyers.

Finally, in October 1966 the 35th Tactical Fighter Wing was moved to Phan Rang AB and took over the units on a permanent basis.

The B-57s, however were transferred almost immediately back to the United States and assigned to the 190th Bombardment Group (Tactical) of the Kansas Air National Guard at Forbes AFB.

The United States had initially been reluctant to equip the Vietnamese Air Force with jet aircraft, since this would be a technical violation of the Geneva Accords and might further escalate the war.

However, the US had already equipped other friendly nations in the region with jet aircraft, and pressure from the government leadership in Saigon coupled with a need to boost the sagging morale of the South Vietnamese people, led to a change of heart.

As the crews completed their training at Clark, they went to Da Nang Air Base and flew combat missions with the 405th's 8th or 13th Bombardment Squadrons, whichever happened to be on station at the time.

Eventually, the VNAF crew members flew in VNAF-marked B-57s, but their combat missions always remained strictly under USAF operational control.

The South Vietnamese government felt at this stage that the VNAF B-57 program should be given some more visibility, and to celebrate Vietnamese Armed Forces Day, on 29 October 1965, five B-57s from the 8th Bombardment Squadron, then based at Da Nang AB, were repainted with VNAF insignia and carried out an air strike against a suspected Viet Cong stronghold and landed Tan Son Nhut Air Base.

To make matters even worse, Major Nguyen Ngoc Bien, the leader of the VNAF B-57 program, was killed in a freak ground accident on 23 February 1966 at Da Nang.

Flights of F-102 interceptors from the 509th Fighter-Interceptor Squadron began to deploy to Tan Son Nhut AB in March 1962 to provide air defense against the unlikely event that North Vietnamese aircraft would attack the South.

They also deployed to Don Muang RTAFB near Bangkok, Thailand and began exchanging rotational duty with the 16th FIS based at Naha AB on Okinawa.

The F-102A was finally withdrawn from Southeast Asia in December 1969 with the phaseout of the aircraft from the USAF inventory, also the clear lack of need for a dedicated air defense interceptor over South Vietnam.

In July 1968, the 315th Air Division reassigned the 463d Tactical Airlift Wing from Mactan Isle Airfield to Clark AB, and it became a tenant unit under the 405th.

The 463d was responsible for operating a C-130 Hercules combat airlift support unit at Tan Son Nhut AB, South Vietnam, and also flew combat support missions within South Vietnam landing and dropping off supplies, equipment and personnel at forward locations throughout the country.

It operated three squadrons of C-130s performing rotational deployments to and from Clark, bringing back wounded personnel with aeromedical airlifts, the aircraft returning to South Vietnam filled with combat supplies and equipment.

The 1st Test Squadron conducted weapons system evaluation (COMBAT SAGE) of repaired battle-damaged F-4 Phantom IIs from 30 April 1970 until the end of the Vietnam War.

During February–March 1973, provided medical, logistical, and administrative support for former prisoners of war, on their way to the United States from North Vietnam.