Vietnam War Medal of Honor Recipient. He received the award posthumously for his actions as a 1st lieutenant with the 5th Special Forces Group (Airborne), 1st Special Forces, Military Assistance Command, Vietnam – Studies and Observations Group, US Army, on February 7, 1967. He served in the US Air Force from 1958 until 1962, After his discharge, he attended Arkansas State University in Jonesboro, Arkansas, and in 1964 he joined the Special Forces branch of the US Army, and was assigned to South Vietnam. On February 7, 1967 his unit came under heavy enemy attack and he organized the defense, rescued a wounded soldier, and single-handedly attacked an enemy position before being mortally wounded at the age of 29. He was the first member of the Military Intelligence Branch to receive the Medal of Honor. In addition to the Medal of Honor, he received the Bronze Star, the Purple Heart, the National Order of Vietnam, the Vietnamese Gallantry Cross, and the Vietnam Campaign Medal, among others. His Medal of Honor citation reads: "For conspicuous gallantry and intrepidity at the risk of his life and above and beyond the call of duty. 1st Lt. Sisler was the platoon leader/adviser to a Special United States/Vietnam exploitation force. While on patrol deep within enemy dominated territory, 1st Lt. Sisler's platoon was attacked from 3 sides by a company sized enemy force. 1st Lt. Sisler quickly rallied his men, deployed them to a better defensive position, called for air strikes, and moved among his men to encourage and direct their efforts. Learning that 2 men had been wounded and were unable to pull back to the perimeter, 1st Lt. Sisler charged from the position through intense enemy fire to assist them. He reached the men and began carrying 1 of them back to the perimeter, when he was taken under more intensive weapons fire by the enemy. Laying down his wounded comrade, he killed 3 onrushing enemy soldiers by firing his rifle and silenced the enemy machinegun with a grenade. As he returned the wounded man to the perimeter, the left flank of the position came under extremely heavy attack by the superior enemy force and several additional men of his platoon were quickly wounded. Realizing the need for instant action to prevent his position from being overrun, 1st Lt. Sisler picked up some grenades and charged single-handedly into the enemy onslaught, firing his weapon and throwing grenades. This singularly heroic action broke up the vicious assault and forced the enemy to begin withdrawing. Despite the continuing enemy fire, 1st Lt. Sisler was moving about the battlefield directing air strikes when he fell mortally wounded. His extraordinary leadership, infinite courage, and selfless concern for his men saved the lives of a number of his comrades. His actions reflect great credit upon himself and uphold the highest traditions of the military service." The light medium speed Naval ship USNS Sisler is named in his honor.