<P> By the end of April, the ARVN collapsed on all fronts except in the Mekong Delta . Thousands of refugees streamed southward, ahead of the main communist onslaught . On 27 April 100,000 North Vietnamese troops encircled Saigon . The city was defended by about 30,000 ARVN troops . To hasten a collapse and foment panic, the NVA shelled the airport and forced its closure . With the air exit closed, large numbers of civilians found that they had no way out . </P> <P> Chaos, unrest, and panic broke out as hysterical South Vietnamese officials and civilians scrambled to leave Saigon . Martial law was declared . American helicopters began evacuating South Vietnamese, U.S., and foreign nationals from various parts of the city and from the U.S. embassy compound . Operation Frequent Wind had been delayed until the last possible moment, because of U.S. Ambassador Graham Martin's belief that Saigon could be held and that a political settlement could be reached . </P> <P> Schlesinger announced early in the morning of 29 April 1975 the evacuation from Saigon by helicopter of the last U.S. diplomatic, military, and civilian personnel . Frequent Wind was arguably the largest helicopter evacuation in history . It began on 29 April, in an atmosphere of desperation, as hysterical crowds of Vietnamese vied for limited space . Martin pleaded with Washington to dispatch $700 million in emergency aid to bolster the regime and help it mobilize fresh military reserves . But American public opinion had soured on this conflict . </P> <P> President Gerald Ford had given a televised speech on 23 April, declaring an end to the Vietnam War and all U.S. aid . Frequent Wind continued around the clock, as North Vietnamese tanks breached defenses on the outskirts of Saigon . In the early morning hours of 30 April, the last U.S. Marines evacuated the embassy by helicopter, as civilians swamped the perimeter and poured into the grounds . Many of them had been employed by the Americans and were left to their fate . </P>

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