After his rookie season with the Steelers, Bleier was drafted into the U.S. Army in December 1968 during the Vietnam War. He volunteered for duty in the South Vietnam and shipped out for Vietnam in May 1969 assigned to Company C, 4th Battalion (Light), 31st Infantry 196th Light Infantry Brigade and assigned as a squad grenadier operating a 40mm M79 grenade launcher. On August 20, while on patrol in Heip Duc, Bleier was wounded in the left thigh by an enemy rifle bullet when his platoon was ambushed in a rice paddy. While he was down, an enemy grenade landed nearby after bouncing off a fellow soldier, sending shrapnel into his lower right leg. He lost part of his right foot in the blast as well. He was later awarded the Bronze Star and Purple Heart. His rank was Specialist 4.
While he was recovering in a hospital in Tokyo, doctors told him that he could not play football again. Soon after, he received a postcard from Steelers owner Art Rooney which read "Rock - the team's not doing well. We need you. Art Rooney". Bleier later said, "When you have somebody take the time and interest to send you a postcard, something that they didn't have to do, you have a special place for those kind of people". After several surgeries, he was discharged from the military in July 1970 and began informal workouts with Steeler teammates