Vietnam ground combat operations in 1965, and at their peak they numbered more than 500,000. The US also engaged in a sustained aerial bombing campaign. Meanwhile, China and the Soviet Union provided North Vietnam with significant material aid and 15,000 combat advisers. Communist forces supplying the Việt Cộng carried supplies along the Hồ Chí Minh trail, which passed through the Kingdom of Laos. The communists attacked South Vietnamese targets during the 1968 Tết Offensive. Although the campaign failed militarily, it shocked the American establishment, and turned US public opinion against the war. During the offensive, communist troops massacred over 3,000 civilians
Cannabis in Vietnam in areas controlled by the Hòa Hảo sect, for fear of driving them to join the National Liberation Front. In the 1960s, the United States government became concerned with cannabis use by US troops in the Vietnam War. Though alcohol was the drug most commonly used by American troops in the Vietnam War, cannabis was the second-most common. Initially rates of usage among deployed soldiers were comparable to those of their stateside peers, with 29% of troops departing Vietnam in 1967 reporting having ever used marijuana in their lives. A 1976 study however showed that from 1967–1971, the proportion of