While serving as a machine gunner with Company C at Fire Support Base Argonne, south of the Demilitarized Zone on March 5, 1969, he was killed in action. He was, along with his 12-man recon team, attacked by enemy fire – mortars, machine guns, and grenades. Jenkins and fellow Marine, Fred Ostrom, took up position in a two-man fighting emplacement. When a hand grenade was thrown into the emplacement, Jenkins leaped on top of Ostrom, shielding him from the explosion and absorbing the full impact of the grenade. He was mortally wounded and posthumously awarded the Medal of Honor for his heroic act and sacrifice of life.