As North Vietnam's 1975 Spring Offensive gained steam, People's Army of Vietnam (PAVN) forces swept through South Vietnam's northern provinces virtually unopposed. Army of the Republic of Vietnam (ARVN) formations defending South Vietnam's Central Highlands region were quickly destroyed, and an attempt to withdraw had degenerated into a complete debacle. In ARVN's I Corps Tactical Zone, which covered the northernmost sector of South Vietnam, units in Hue and Da Nang had simply dissolved with no resistance.
The North Vietnamese Politburo had only planned the Spring Offensive as a preparatory phase for the launching of a general offensive in the following year. Having observed the stunning collapse of the South Vietnamese Army in Hue and Da Nang, they made a drastic change in plans. Instead of waiting for the following year, in accordance with a long-standing doctrine of finely detailed planning and methodical battlefield preparation, they would immediately begin a final drive on Saigon, South Vietnam's capital city. Their preliminary focus was set on the strategic road junction town of Xuan Loc, the capital of Long Khanh province.
Hanoi Prepares to Deliver a Final Blow
Xuan Loc, located 60 kilometers northeast of Saigon, lay before the vital intersection of Route 1 and Route 20, the two main highways connecting the center of the country with Saigon. With the conquest of South Vietnam's two northern military regions in March, the town had suddenly become a critical node on the improvised defensive line around Saigon formed by the desperate South Vietnamese army. If ARVN could make a successful stand at Xuan Loc, there remained a chance for the situation to be stabilized and for units to be regrouped, saving the country from defeat.
The communist leadership in Hanoi was determined to prevent the South Vietnamese from recovering, and perceived an opportunity to end the war quickly with an attack on Saigon via Xuan Loc. Another hard blow might cause the last vestiges of ARVN resistance to crumble, opening the gateway to Saigon. The entire 4th Army Corps, one of the four regular army corps of the People's Army of Vietnam and comprised of three divisions, was sent to Xuan Loc to vanquish the 18th Division of the Army of the Republic of Vietnam.
The Epic Last Stand of ARVN's 18th Infantry Division
As dawn arrived on April 19, 1975, the clanking of steel tank treads followed by waves of North Vietnamese infantry heralded the beginning of the final battle for the capital city of South Vietnam. Despite the tremendous military setbacks suffered by South Vietnam in early 1975, the 18th ARVN Infantry Division under the command of Brigadier General Le Minh Dao did not crumble, and Hanoi's dreams of an easy victory evaporated in the fires of what the North Vietnamese commander called the fiercest battle of his 30-year military career.
PAVN units moving down from the north were forced to stop when ARVN elements counterattacked from the south. Throughout April 9, the ARVN 18th Division staged counterattacks on the PAVN flanks to slow down their momentum. Between April 10 and 11, PAVN tried to destroy the ARVN defenders of Xuan Loc but on each attempt they were forced redirect their energies to fending off counterattacks on their flanks. During those two days, the South Vietnamese Air Force flew more than 200 bombing sorties in support of the 18th Division.
On April 12, the South Vietnamese General Staff decided to reinforce the defenders of Xuan Loc with units from the ARVN general reserve. As the reinforcements were arriving, South Vietnamese fighter-bombers taking off from the air bases at Bien Hoa and Tan Son Nhat flew between 80 and 120 sorties per day in support. The tide began to turn in favor of the North Vietnamese on April 15 when, instead of shelling Xuan Loc, PAVN artillery began pounding Bien Hoa. Within a day, the Republic of Vietnam Air Force 3d Air Division, whose headquarters were at Bien Hoa, was forced by continuous North Vietnamese artillery bombardment to cease all operations.
By April 18, the North Vietnamese had succeeded in completely isolating Xuan Loc. The South Vietnamese 18th Division had been cut off from reinforcements and was surrounded by the PAVN 4th Army Corps. On April 19, the ARVN General Staff ordered General Le Minh Dao to evacuate Xuan Loc. By the end of April 21, Xuan Loc was under North Vietnamese control and the road to Saigon was open.
The Resignation of Nguyen Van Thieu
Having captured Xuan Loc, albeit at a heavy cost, the People's Army of Vietnam now effectively controlled two-thirds of South Vietnamese territory. The Army of the Republic of Vietnam had lost almost every unit from its general reserve in trying to prevent this defeat. On April 18, the commander of the ARVN III Corps informed President Thieu that Xuan Loc had been lost and that South Vietnamese armed forces only retained strength to hold out for a few more days.
On the morning of April 21, 1975, having learned that Xuan Loc had fallen and subjected to intense political pressure, South Vietnamese President Nguyen Van Thieu officially resigned from his position. Thieu had gambled what remained of his political career on a final vain effort to save South Vietnam by sending the last remaining units of the South Vietnamese army to Xuan Loc.