In the late 1960s he served with the 1st Cavalry Division, first as chief of staff, then as commander of 2nd Brigade, and later as assistant division commander. He served as the Chief of Staff of 2nd Brigade, 1st Air Cavalry Division, in South Vietnam, from September 1966 to October 1967.
Casey served with U.S. Army Combat Developments Command at Fort Belvoir, Virginia, from October 1967 to August 1968, and then as Commanding General of the U.S. Army Combat Developments Command Combat Arms Group at Fort Leavenworth, Kansas, from September 1968 to July 1969. While home on leave from serving in Vietnam, he was promoted to major general during a ceremony on April 30, 1970, at the Pentagon. In May 1970, he assumed command of the 1st Cavalry Division in Vietnam.
Death
On July 7, 1970, he was killed in a helicopter crash in South Vietnam when the UH-1H Huey helicopter he was co-piloting hit a mountain due to poor weather near Bao Luc as he was en route to Cam Ranh to visit wounded troops, before they were transported to Japan for medical treatment.[3] Seven men died in the crash.[4] The wreckage of the helicopter was found within days.
