During the spring season of 1975, the PAVN High Command in Hanoi made the decision to seize the major South Vietnamese cities of Huế and Da Nang, and also destroy the various South Vietnamese units in I Corps Tactical Zone, led by ARVN General Ngô Quang Trưởng. Originally, the campaign was planned to take place over two phases; during the seasons of spring-summer and autumn. However, as the North Vietnamese forces rolled over South Vietnamese defences on the outskirts of Huế and Da Nang, President Nguyễn Văn Thiệu ordered General Trưởng to abandon all territories under his control, and pull his forces back to the coastal areas of I Corps. The South Vietnamese withdrawal quickly turned into a rout, as the PAVN 2nd Army Corps picked off one South Vietnamese unit after another, until Huế and Da Nang were completely surrounded. By March 29, 1975, PAVN troops had full control of Huế and Da Nang, while South Vietnam lost all territories and most of the units belonging to I Corps.

The fall of Huế and Da Nang did not spell the end of the misery suffered by the ARVN. On March 31, ARVN General Phạm Văn Phú—commander of II Corps Tactical Zone—attempted to form a new defensive line from Qui Nhơn to cover the retreat of the ARVN 22nd Infantry Division, but they too were destroyed by the PAVN. By April 2, South Vietnam had lost control of the northern provinces, as well as two army corps.