Vietnam War Medal of Honor Recipient. He received the award posthumously (presented to his family) from President Richard M. Nixon at the White House on February 16, 1971, for his actions as a specialist fourth class with Company D, 1st Battalion, 8th Cavalry, 1st Cavalry Division, US Army, on March 21, 1969, in Tay Ninh Province, South Vietnam. After graduating from high school, he joined the US Army in 1968 and following his combat training, he was sent to South Vietnam. On that day, while performing duties as a mortarman during Operation Toan Thang III, he smothered the blasts of three enemy-thrown explosives with his body, sacrificing his life to protect those around him. He was also awarded the Purple Heart. His Medal of Honor citation reads: "For conspicuous gallantry and intrepidity in action at the risk of his life above and beyond the call of duty. Sp4c. Johnston distinguished himself while serving as a mortarman with Company D, at a fire support base in Tay Ninh Province. Sp4c. Johnston's company was in defense positions when it came under a devastating rocket and mortar attack. Under cover of the bombardment, enemy sappers broke through the defensive perimeter and began hurling explosive charges into the main defensive bunkers. Sp4c. Johnston and six of his comrades had moved from their exposed position to one of the bunkers to continue their fight against the enemy attackers. As they were firing from the bunker, an enemy soldier threw three explosive charges into their position. Sensing the danger to his comrades, Sp4c. Johnston, with complete disregard for his safety, hurled himself onto the explosive charges, smothering the detonations with his body and shielding his fellow soldiers from the blast. His heroic action saved the lives of six of his comrades. Sp4c. Johnston's concern for his fellow men at the cost of his life were in the highest traditions of the military service and reflect great credit upon himself, his unit, and the U.S. Army."