Commissioned into the Royal Marines in ’05, he spent his early career in 42 Commando RM and at the Commando Training Centre Lympstone, as a Recruit Instructor. He served as 2 nd in Command (2ic) of a Company in 40 Commando and as 2ic of Commando Training Wing (CTW). In ‘16/17 he had the privilege of commanding a sub-unit of 45 Commando Group, this included a period of 6 months on Op SILVAN, conducting Maritime Interdiction Operations (MIOPS) in support of the UK Border Force in the Mediterranean.

He has enjoyed a variety of staff appointments including Navy Command Headquarters, as a J1/7 (Personnel & Capability) desk officer including emerging capabilities such as the Armoured Support (AS) specialisation, the RM component of the Special Forces Support Group (SFSG) and the Maritime Manoeuvre Squadron at RM Poole. He has served as Directing Staff (DS) at the Infantry Battle School Platoon Commanders Battle Course (PCBC), at Headquarters 3 Commando Brigade, and at the Defence Academy as DS in the Naval Division, Army Division and on ACSC. He recently completed 3 hugely rewarding years as the of Chief of Staff of the Higher Command and Staff Course (HCSC), the UKs senior operational focussed educational intervention, before assuming his role as the Operational Planning Team (JEF) and Acting Assistant Chief of Staff JEF in Sept ’24.

His operational experience includes several Amphibious Ready Group (ARG) deployments, and 3 operational deployments to Afghanistan. He was embedded with US forces during Op SHADER as the Deputy Chief Future Operations in Iraq, and as Chief of Future Operations in the Military Coordination Cell (MCG-SOM), Somalia, were he provided military and security advice to the Prime Minister of Somalia. He has also planned and been deployed on a range of high-risk contingency operations in Africa and the Middle East. He was appointed MBE for operational service in Somalia, and had previously been awarded the US Defense Meritorious Service Medal.

Lt Col O’Callaghan holds an MA in Security Studies from King’s College London, a Post Graduate Diploma in Strategic Management from Stratford, and a Post Graduate Certificate in Education from Plymouth University. He is currently researching for a PhD in Imperial German Navy and Royal Navy learning and adaptation during the Great War. In ’20 he was awarded the ‘Best Educator Award’ by the Worshipful Company of Educators.

He is married to Melanie, a self-employed linguist, and they have 2 sons Benjamin (15) and Reuben (13). They live in Exmouth, close to the sea.