<P> Vietnamization received another severe test in the spring of 1972 when the North Vietnamese launched a massive conventional offensive across the Demilitarized Zone . Beginning on March 30, the Easter Offensive (known as the Nguyễn Huệ Offensive to the North Vietnamese) quickly overran the three northernmost provinces of South Vietnam, including the provincial capital of Quảng Trị City . PAVN forces then drove south toward Huế . </P> <P> Early in April, PAVN opened two additional operations . The first, a three - division thrust supported by tanks and heavy artillery, advanced out of Cambodia on April 5 . The North Vietnamese seized the town of Loc Ninh and advanced toward the provincial capital of An Lộc in Bình Long Province . The second new offensive, launched from the tri-border region into the Central Highlands, seized a complex of ARVN outposts near Dak To and then advanced toward Kon Tum, threatening to split South Vietnam in two . </P> <P> The U.S. countered with a buildup of American airpower to support ARVN defensive operations and to conduct Operation Linebacker, the first offensive bombing of North Vietnam since Rolling Thunder had been terminated in 1968 . The PAVN attacks against Huế, An Lộc, and Kon Tum were contained and the ARVN launched a counteroffensive in May to retake the lost northern provinces . On September 10, the South Vietnamese flag once again flew over the ruins of the Citadel of Quảng Trị City, but the ARVN offensive then ran out of steam, conceding the rest of the occupied territory to the North Vietnamese . South Vietnam had countered the heaviest attack since Tet, but it was very evident that it was totally dependent on U.S. airpower for its survival . Meanwhile, the withdrawal of American troops, who numbered less than 100,000 at the beginning of the year, was continued as scheduled . By June only six infantry battalions remained . On August 12, the last American ground combat division left the country . However, the U.S. continued to operate the base At Long Binh . Combat patrols continued there until November 11 when the U.S. handed over the base to the South Vietnamese . After this, only 24,000 American troops remained in Vietnam and President Nixon announced that they would stay there until all U.S. POW's were freed . </P> <P> At the beginning of the North Vietnamese invasion, the media, including conservative commentator William F. Buckley, predicted the downfall of the Republic of Vietnam; Buckley even called for the firing of General Creighton Abrams as an incompetent military leader . But the ARVN succeeded in defeating General Giap and his huge invading army . His forces were shattered at the Battle of An Lộc, where he threw several divisions at the entrenched South Vietnamese forces, ultimately losing over half of his army as casualties . General Giap's loss and subsequent retreat was viewed as so great a failure by the North Vietnamese Communist Party that Giap was relieved of his command . Although ARVN troops withstood and repelled the massive PAVN attack at An Lộc, American air power seems to have been a key to the ARVN success, just as it had been a key factor in supporting U.S. ground forces when they operated in South Vietnam prior to 1972 . Thus, the 1973 withdrawal of U.S. military support and passage of Congressional resolutions cutting off U.S. funding for combat activities in Indochina (H.R. 9055 and H.J. Res. 636) opened the way for the 1975 defeat of the Republic of Vietnam . </P>

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