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. Thieu agreed that Trưởng should attempt to hold Huế despite misgivings as to the ARVN's ability to hold the city and the navy's ability to supply them. Trưởng returned to Da Nang to reorganise his forces for the defense of Huế but was immediately confronted with a PAVN frontal assault against Quảng Trị Province and the ARVN soon retreated towards Huế. On 21 March the PAVN launched attacks south of Huế aimed at isolating the city and preventing the reinforcement or withdrawal or ARVN forces into the city and establishment of defensive lines. On 22 March Thieu ordered the withdrawal of all ARVN forces between Huế and Da Nang to fall back into an enclave at Da Nang.