The United Kingdom and Ireland have signed a refreshed Memorandum of Understanding (MoU) on bilateral defence cooperation, replacing an agreement that had been in place since 2015. The signing took place on 13 March 2026 at Fota House in Cork, during the second UK-Ireland Leaders’ Summit.
The Secretary of State for Defence, John Healey MP, and Irish Minister for Defence, Helen McEntee TD, signed the updated MoU, which focuses on enhanced maritime cooperation, cyber defence, air domain information sharing, and increased joint procurement.
The refreshed MoU will see the UK Armed Forces and the Irish Defence Forces strengthen their maritime security cooperation to better protect critical undersea infrastructure and develop improved response mechanisms to maritime security incidents. Both governments will also explore opportunities for joint procurement of military equipment and new government-to-government sales. In the air and cyber domains, both sides will boost information sharing, improve joint situational awareness, and increase resilience against threats.
The MoU also emphasises continued collaboration in UN peacekeeping, crisis management, and humanitarian operations; enhanced cooperation on training and military education exchanges; and ongoing support for joint opportunities in Ukraine as members of the Coalition of the Willing.
Members of the Defence Forces attend a wide range of courses in the UK, and members of the UK Forces have attended courses in Ireland, including at the UN School and on Command and Staff Courses.
Alongside the MoU, both governments agreed on a separate measure directly addressing undersea threats. A new Subsea Infrastructure Bilateral Collaboration Framework was established, enabling information sharing and coordinated response mechanisms for addressing major subsea communication cable incidents. A series of live exercises will be carried out to test readiness, with the first scheduled for September 2026.
UK Defence Secretary John Healey MP said in his official statement:
“The UK and Ireland share a long history of defence cooperation — from crisis management and humanitarian operations to training, military education, and staff exchanges. This rebooted Memorandum of Understanding modernises our framework for cooperation on areas critical to both our nations’ security, particularly in countering the growing undersea and cyber threats we share.”
Irish Minister for Defence Helen McEntee TD said in the Irish Government’s official press release:
“It is appropriate that, after ten years, we take the opportunity to refresh our Memorandum of Understanding and provide for a particular focus in such areas as maritime, cyber defence and security, air (information sharing), and joint procurement initiatives.”
Joint Statement from Both Leaders
The MoU formed part of a broader joint statement published by both governments following the summit. On security and the shared seas, Prime Minister Starmer and Taoiseach Martin stated:
“In a more contested environment, with increased hostile state activity, we are enhancing information sharing, maritime domain awareness, and coordinated defence planning to better detect, deter, and respond to threats across the Irish Sea and North-East Atlantic, including updating our MoU on defence. This also underscores our commitment to strengthening wider European and Euro-Atlantic security.”
