Born and raised in Cork, Billy became an Irish Army Infantry Officer in 2003. His Irish military service included overseas deployments to Chad and Bosnia and service in the Irish Special Forces' Army Ranger Wing, where he served as a platoon commander from 2010–2013. Billy holds a vast range of specialist military qualifications including military freefall, survival, recon and advanced mountaineering. He retired from the Irish Army in 2014 in order to transfer his service to the Australian Army. He holds an Honours Degree in Physical Education from the University of Limerick, has summitted Mount Kilimanjaro for charity and is currently an Officer in the Australian Infantry.