 He was assigned to the 1st Battalion, 9th Marine Regiment and on November 13, he was assigned to Company A, 1st Battalion, 9th Marine Regiment, 3rd Marine Division as a supply sergeant.On December 11, he and his unit arrived in South Vietnam from Okinawa (under service regulations, only one brother was allowed to go to Vietnam).On March 24, 1967, the 1st Battalion, 9th Marines began Operation Prairie III; that same day, in the Gio Linh District, Quang Tri Province, Sergeant Singleton's Company A came under intense enemy fire at the village of Phu An.