As part of these purges, in 1963 the South Vietnamese commandos killed Trung's father and arrested his mother; the rest of the family were subjected to intimidation and had their homes burned.

Trung was continuing his education when in 1968 the Tet Offensive occurred, disrupting Saigon and causing South Vietnam to increase conscription requirements.

While in the US, Trung was able to remain in contact with his North Vietnamese handlers, successfully recording technical information on American aircraft and tactics in personal correspondence he mailed back to Vietnam.

[1] By 1975 Trung had returned to Vietnam and was conducting training missions with newer pilots, holding the rank of first lieutenant and commanding a squadron of ground attack aircraft.

After departing Bến Tre, Trung flew his Northrop F-5 towards Saigon and dropped his payload on Independence Palace, the South Vietnamese presidential residence, striking the building with all four bombs but causing only minor damage.

[1] Trung's bombing of Independence Palace had caused only minor damage, but his actions were celebrated in North Vietnam, was widely covered in Western media, and constituted a major blow to South Vietnamese morale.

On 28 April, the squadron launched a highly successful airstrike on Tan Son Nhut Air Base, during which Trung was second in command and piloted the lead aircraft.

In addition, the attack was a major factor in the United States deciding to scrap its planned evacuation of Saigon via fixed wing aircraft in favor of using helicopters in Operation Frequent Wind.