reports while avoiding guerrilla fighters. A total of 900 fragging and suspected fragging incidents were investigated, most occurring between 1969 and 1971. In 1969, field-performance of the U.S. Forces was characterised by lowered morale, lack of motivation, and poor leadership. The significant decline in U.S. morale was demonstrated by the Battle of FSB Mary Ann in March 1971, in which a sapper attack inflicted serious losses on the U.S. defenders. William Westmoreland, no longer in command but tasked with investigation of the failure, cited a clear dereliction of duty, lax defensive postures and lack of officers in charge as its cause. On the collapse of U.S. morale, historian Shelby Stanton wrote: ARVN taking the lead and U.S. ground-force withdrawal Beginning in 1970, American troops were withdrawn from border areas where most of the fighting took place and instead redeployed along the coast and interior. US casualties in 1970 were less than half of 1969 casualties after being relegated to less active combat. While U.S. forces were redeployed, the ARVN took over combat operations throughout the country, with casualties double US casualties in 1969, and more than triple US ones in 1970. In the post-Tet environment, membership in the South Vietnamese Regional Force and Popular Force militias grew, and they were now more capable of providing village security, which the Americans had not accomplished 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, Viet Cong forces were no longer southern-majority, as nearly 70% of units were northerners. Between 1969 and 1971 the Viet Cong and some PAVN units had reverted to small unit tactics typical of 1967 and prior instead of nationwide 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. Cambodia Prince Norodom Sihanouk had proclaimed Cambodia neutral since 1955, but permitted the PAVN/Viet Cong to use the port of Sihanoukville and the Sihanouk Trail. In March 1969 Nixon launched a massive secret bombing campaign, called Operation Menu, against communist sanctuaries along the Cambodia/Vietnam border. Only five high-ranking congressional officials were informed of Operation