Moving out of eastern Cambodia, North Vietnamese troops open the second front of their offensive with a drive into Binh Long Province, attacking Loc Ninh, a border town 75 miles north of Saigon on Highway 13. At the same time, additional North Vietnamese cut the highway between An Loc, the provincial capital, and Saigon to the south, effectively isolating An Loc from outside support.
This attack was the southernmost thrust of the three-pronged Nguyen Hue Offensive (later known as the "Easter Offensive"), a massive invasion by North Vietnamese forces designed to strike the blow that would win them the war. The attacking force included 14 infantry divisions and 26 separate regiments, with more than 120,000 troops and approximately 1,200 tanks and other armored vehicles. The main North Vietnamese objectives, in addition to An Loc in the south, were Quang Tri in the north, and Kontum in the Central Highlands. Initially, the South Vietnamese defenders in each case were almost overwhelmed, particularly in the northernmost provinces where government forces abandoned their positions in Quang Tri and fled south in the face of the enemy onslaught.
In Binh Long, the North Vietnamese forces crossed into South Vietnam from Cambodia to strike first at Loc Ninh, then quickly encircled An Loc, holding it under siege for almost three months while they made repeated attempts to take the city. The defenders suffered heavy casualties, including 2,300 dead or missing, but with the aid of U.S. advisors and American airpower, they managed to hold An Loc against vastly superior odds until the siege was lifted on June 18. Fighting continued all over South Vietnam into the summer months, but eventually the South Vietnamese forces prevailed against the invaders and they retook Quang Tri in September. With the communist invasion blunted, President Nixon declared that the South Vietnamese victory proved the viability of his Vietnamization program, which he had instituted in 1969 to increase the combat capability of the South Vietnamese armed forces.