, and the destroyers and conducted a brief night raid against the North Vietnamese forces protecting the port of Haiphong. After the bombardment, the ships were threatened by four Soviet-built torpedo boats. Joined by two aircraft from the USS Coral Sea, three of the four torpedo boats were sunk. It was one of the few ship-to-ship naval battles of the war. Paris Peace Talks and conclusion The stalled offensive in the South and the devastation in North Vietnam had helped to convince Hanoi to return to the bargaining table by early August. The meetings produced new concessions from Hanoi which promised to end the deadlock that had plagued negotiations since their inception in 1968. Gone were Hanoi's demands for the ouster of South Vietnamese President Nguyễn Văn Thiệu and his replacement by a coalition government in which the Viet Cong would participate. The U.S. on its part agreed to a cease fire in place which conceded that PAVN soldiers could remain in South Vietnam after a peace agreement. The diplomatic impasse was broken and Nixon ordered a halt to all bombing above the 20th parallel on 23 October and on 26 October Kissinger announced that "peace is at hand." This once again placed Hanoi and Haiphong off-limits, and halted Linebacker operations. Air Force historian Earl Tilford has written that Linebacker was "a watershed in aerial warfare...it was the first modern aerial campaign in which precision guided munitions changed the way in which air power was used." It succeeded, where Rolling Thunder had failed, he claimed, for three reasons: Nixon was decisive in his actions and gave the military greater latitude in targeting; American airpower was forcefully and appropriately used; and the immense difference in the technology utilized made Linebacker the first bombing campaign in a "new era" of aerial warfare. During and immediately following the PAVN offensive, U.S. Air Force, Navy and Marine Corps aviators had flown 18,000 sorties in the four northern provinces of South Vietnam and dropped 40,000 tons of ordnance in the Battle of An Lộc. Between March and May, B-52 sortie rates had climbed from 700 to 2,200 per month and they had dropped 57,000 tons of bombs in Quảng Trị Province alone. During Freedom Train and Linebacker proper, B-52s had dropped 150,237 tons of bombs on the North while Air Force and Navy tactical aircraft had flown 1,216 sorties and dropped another 5,000 tons of