Anthony Paul O’Reilly was born in Galway, Ireland to Patrick Joseph O’Reilly and Mary Kate O’Shaughnessy on 1 June 1938. He had five siblings and grew up in Galway. His father died when Anthony was 17. Anthony left Galway for the United States where he enlisted in the U. S. Army. He became airborne qualified and was commissioned a lieutenant before he was assigned to Vietnam. On his 30th birthday he was serving as commander of an infantry company during an operation near the Cambodian border. Below is an excerpt from the citation for the Distinguish Service Cross (DSC) that he earned:

"A sister company was pinned down by an estimated battalion of Viet Cong firing small arms, machine guns, rockets and mortars from a well-fortified bunker complex. Lieutenant O’Reilly attempted to lead his force to the beleaguered unit but was stopped by the enemy’s barrage. Disregarding his safety, he crawled twenty-five meters toward the nearest bunker and hurled grenades into it which killed its two occupants and silenced its deadly stream of automatic weapons fire. He then sprang to his feet and rallied his men for an assault on the remaining fortifications. In fierce close combat the Viet Cong abandoned their emplacements and broke contact. On 3 June 1968 contact was made again. As his unit came under intense automatic weapons fire, Lieutenant O’Reilly quickly moved his troops on-line and assaulted the hostile positions. While deploying his men so they could effectively engage the Viet Cong bunkers with comparative safety, he was killed by a burst of enemy automatic weapons fire".