World War II Medal of Honor Recipient. He served during World War II in the United States Marine Corps as a Gunnery Sergeant in Company G, 3rd Battalion, 27th Marines, 5th Marine Division. He was awarded the Medal of Honor for his bravery during the Marine Corps assault on Iwo Jima in the Volcano Islands on February 27, 1945. His citation reads "For extraordinary gallantry and intrepidity at the risk of his life above and beyond the call of duty as leader of an assault platoon in action against enemy Japanese forces. With the advance of his company toward Hill 362 disrupted by vicious machinegun fire from a forward position which guarded the approaches to this key enemy stronghold, G/Sgt. Walsh fearlessly charged at the head of his platoon against the Japanese entrenched on the ridge above him, utterly oblivious to the unrelenting fury of hostile automatic weapons fire and handgrenades employed with fanatic desperation to smash his daring assault. Thrown back by the enemy's savage resistance, he once again led his men in a seemingly impossible attack up the steep, rocky slope, boldly defiant of the annihilating streams of bullets which saturated the area. Despite his own casualty losses and the overwhelming advantage held by the Japanese in superior numbers and dominant position, he gained the ridge's top only to be subjected to an intense barrage of handgrenades thrown by the remaining Japanese staging a suicidal last stand on the reverse slope. When 1 of the grenades fell in the midst of his surviving men, huddled together in a small trench, G/Sgt. Walsh, in a final valiant act of complete self-sacrifice, instantly threw himself upon the deadly bomb, absorbing with his own body the full and terrific force of the explosion. Through his extraordinary initiative and inspiring valor in the face of almost certain death, he saved his comrades from injury and possible loss of life and enabled his company to seize and hold this vital enemy position. He gallantly gave his life for his country". He was one of 27 Marines to be awarded the Medal of Honor for bravery on Iwo Jima, and one of the 12 posthumous recipients.