Career
Mangan joined the Defence Forces as a cadet in 1960 and is cited as having "overseen major strategic initiatives in the key areas of state defence, provision of peace support and government support services, equipment and infrastructual modernisations programmes and human resource management."
He oversaw the deployment of Irish troops to East Timor (1999–2002), Kosovo (since 1999), Eritrea 2001-2003 and Liberia (since 2003). He was awarded the Legion of Merit by the United States of America in September 2003, and the Cross of Honor in Gold by Germany in January 2004. He was succeeded by Lieutenant
General James Sreenan in February 2004.
