 On 11 March 1975, faced with the PAVN invasion and the collapse of the South Vietnamese positions in the Central Highlands, President Nguyen Van Thieu decided on a new strategy of "Light at the top, heavy on the bottom" which essentially involved only defending III Corps and IV Corps, with the ARVN withdrawing from I Corps and II Corps as necessary in the face of PAVN pressure.Thieu met with Lieutenant General Ngô Quang Trưởng in Saigon on 13 March and Trưởng understood that he was authorised to concentrate his forces around Da Nang.On 19 March Trưởng presented Thieu with alternative plans for the simultaneous withdrawal by road from Huế, Chu Lai and Qui Nhơn to Da Nang or if the road was cut by the PAVN for withdrawal of forces into enclaves at Huế, Chu Lai and Qui Nhơn and then their evacuation by sea.