At the start of 1971 South Vietnamese troops continued operations against [[NVA) and Vietcong (VC) base areas in eastern Cambodia. The ill-conceived and poorly executed Operation Lam Son 719 against NVA supply lines in eastern Laos showed the weaknesses within the South Vietnamese military command and the limited ability of South Vietnam's armed forces to conduct large-scale combined arms operations. The U.S. continued its unilateral withdrawal from South Vietnam despite the lack of any progress in the Paris Peace Talks and by November U.S. forces had ceased offensive operations. The U.S. withdrawal and antiwar sentiment within the military led to an ongoing decline in morale and discipline within the U.S. forces and growing drug use, particularly of heroin. As U.S. combat units withdrew,