Brigadier General Brennan was born in 1958 and joined the Defence Forces as a cadet with the 53rd Cadel Class in 1976. Brigadier General Brennan is married to Maura and they have three children: Nicola, Adam and Cathal.
On commissioning in 1978, Brigadier General Brennan was assigned to the Infantry Corps and began his career with the 12 Infantry Battalion, in Limerick and Clonmel. Throughout his career, Brigadier General Brennan has served in key command and staff appointments at Battalion, Brigade and Defence Force Headquarter level. Among these key appointments have been Instructor Command and Staff School, the Military College, Defence Forces Training Centre, Curragh and Officer Commanding 3 Infantry Battalion, Stephens Barracks, Kilkenny and more recently as Director of Operations and Plans for the Defence Forces.
Brigadier General Brennan has extensive overseas experience, with the United Nations in Lebanon as Battalion Commander 105 Infantry Battalion (2011/2012) and as Deputy Commander, Multinational Task Force Sector West (2013). He has also served in Angola and in Brussels where he was seconded to the European Union Council as part of the EU Military Staff between 2007 and 2010. He was appointed to Brussels in 2018.
Brigadier General Brennan was educated in the De La Salle, Bagenalstown, Carlow and Patrician College, Ballyfin, Laois. His military training includes Command and Staff Courses in the Military College, Curragh and with the United States Army at Fort Leavenworth, Kansas. He is a graduate of NUIG, DCU (Oscail) and NUIM, where he graduated with a Bachelor of Commerce Degree, a Diploma in Information Technology, and a Masters of Arts in Management, Leadership and Defence Studies respectively.
Brigadier General Brennan who lives in Cashel Downs, Kilkenny City is a native of Paulstown, Co Kilkenny and has a keen interest in sports.