<P> On the collapse of US morale, historian Shelby Stanton wrote: </P> <P> In the last years of the Army's retreat, its remaining forces were relegated to static security . The American Army's decline was readily apparent in this final stage . Racial incidents, drug abuse, combat disobedience, and crime reflected growing idleness, resentment, and frustration...the fatal handicaps of faulty campaign strategy, incomplete wartime preparation, and the tardy, superficial attempts at Vietnamization . An entire American army was sacrificed on the battlefield of Vietnam . </P> <P> Beginning in 1970, American troops were withdrawn from border areas where most of the fighting took place, instead redeployed along the coast and interior, and US casualties in 1970 were less than half of 1969 casualties after being relegated to less active combat . At the same time that US forces were deployed, the Army of the Republic of Vietnam took over combat operations throughout the country, with casualties doubled US casualties in 1969, and more than tripled US ones in 1970 . The post-Tet environment saw a rise in membership in Regional Force and Popular Force militias, now more capable of providing village security which the Americans could not under Westmoreland . In 1970 Nixon announced the withdrawal of an additional 150,000 American troops, reducing the number of Americans to 265,500 . By 1970 the Viet Cong forces were no - longer southern - majority, and nearly 70% of units were northerners . Between 1969 to 1971 the Viet Cong and some PAVN units had reverted to small unit tactics typical of 1967 and prior instead of nation - wide grand offensives . In 1971 Australia and New Zealand withdrew their soldiers and U.S. troop count was further reduced to 196,700, with a deadline to remove another 45,000 troops by February 1972 . The United States also reduced support troops and in March 1971 the 5th Special Forces Group, the first American unit deployed to South Vietnam, withdrew to Fort Bragg, North Carolina . </P> <P> Prince Norodom Sihanouk had proclaimed Cambodia neutral since 1955, but permitted the PAVN / NLF to use Cambodia as a staging ground for the Sihanouk Trail . Nixon had by then launched a massive bombing campaign, called Operation Menu, against communist sanctuaries along the Cambodia / Vietnam border . Only five high - ranking Congressional officials were informed of Operation Menu . </P>

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