Vessey was promoted to brigadier general in 1970, and assigned as commander of U.S. Army Supply Thailand, a logistics support area for soldiers serving in Vietnam. He commanded U.S. military activities in Laos from 1973 to 1974, when he was promoted to major general as commander of the 4th Infantry Division. In 1975, Vessey was promoted to lieutenant general and assigned as the Army's deputy chief of staff for operations and plans, G-3. He was promoted to general in 1976, and named to command United States Forces Korea and the Eighth United States Army. In 1978, Vessey also assumed command of the Republic of Korea-United States Combined Forces Command. He served in Korea until 1979, when he was assigned as Vice Chief of Staff of the United States Army.