 In December, 1968 Rees was assigned to Vietnam, serving as Assistant Training and Operations Officer (S3 Air) for 2nd Battalion, 17th Cavalry Regiment, 101st Airborne Division and commander of Troop D, 2nd Battalion, 17th Cavalry.After returning to the United States, Rees completed training as an Army Aviator.From March, 1972 to August, 1973 he was assigned to 1st Battalion, 17th Cavalry Regiment, 82nd Airborne Division.