onslaught, and its forces collapsed on 11 March. Once again, Hanoi was surprised by the speed of their success. Dung now urged the Politburo to allow him to seize Pleiku immediately and then turn his attention to Kon Tum. He argued that with two months of good weather remaining until the onset of the monsoon, it would be irresponsible to not take advantage of the situation. President Thiệu, a former general, was fearful that his forces would be cut off in the north by the attacking communists; Thieu ordered a retreat, which soon turned into a bloody rout. While the bulk of ARVN forces attempted to flee, isolated units fought desperately. ARVN general Phu abandoned Pleiku and Kon Tum and retreated toward the coast, in what became known as the "column of tears". On 20 March, Thieu reversed himself and ordered Huế, Vietnam's third-largest city, be held at all costs, and then changed his policy several times. As the PAVN launched their attack, panic set in, and ARVN resistance withered. On 22 March, the PAVN opened the siege of Huế. Civilians flooded the airport and the docks hoping for any mode of escape. As resistance in Huế collapsed, PAVN rockets rained down on Da Nang and its airport. By 28 March 35,000 PAVN troops were poised to attack the suburbs. By 30 March 100,000 leaderless ARVN troops surrendered as the PAVN marched victoriously through Da Nang. With the fall of the city, the defense of the Central Highlands and Northern provinces came to an end. Final North Vietnamese offensive With the northern half of the country under their control, the Politburo ordered General Dung to launch the final offensive against Saigon. The operational plan for the Ho Chi Minh Campaign called for the capture of Saigon before 1 May. Hanoi wished to avoid the coming monsoon and prevent any redeployment of ARVN forces defending the capital. Northern forces, their morale boosted by their recent victories, rolled on, taking Nha Trang, Cam Ranh and Da Lat. On 7 April, three PAVN divisions attacked Xuân Lộc, east of Saigon. For two bloody weeks, severe fighting raged as the ARVN defenders made a last stand to try to block the PAVN advance. On 21 April, however, the exhausted garrison was ordered to withdraw towards Saigon. An embittered and tearful president Thieu resigned on the same day, declaring that the United States had betrayed