Lancaster House 2.0: Declaration on Modernising UK-French Defence and Security Cooperation
Source: gov.uk (2025-07-10)

Declaration on Modernising UK-French Defence and Security Cooperation.

The UK and France, as Europe’s only nuclear powers and leading militaries, share a unique responsibility for European and international defence and security. Our two nations represent nearly 40% of the defence budget of European Allies, and more than 50% of European spending on research and technology.

Since the Chequers Declaration in 1995, successive generations of leaders have recognised the intertwined nature of our vital interests, affirming that a threat to one would represent a threat against the other. In 2010, through the Lancaster House Treaties, our nations formalised this shared cooperation to address the challenges of that era: expeditionary warfare and counterterrorism.

Fifteen years later, the threats we face have changed fundamentally with state-on-state conflict rising globally and, since Russia’s illegal invasion of Ukraine, the return of full-scale war to Europe. We have a shared responsibility to strengthen Euro-Atlantic security and recall, in this regard, the critical deterrence that NATO provides. We reaffirm the importance of intensifying our efforts in support of NATO and acting jointly within it. We also recognise the value of a stronger and more capable European defence that contributes positively to transatlantic and global security and is complementary to, and interoperable with, NATO. In this regard, we underline that the European Union remains a unique and essential partner for NATO. We also welcome the progress we have made on the UK-EU Security Defence Partnership in bringing together our shared interests in protecting the continent.

The UK and France share the same understanding of the threats we face. The return of conventional warfighting at scale in Europe and beyond, strategic competition on the global stage, combined with hostile state activity, rapid expansion in hybrid warfare and disinformation, create a febrile and dangerous international order. States are increasingly using hybrid tactics against us, either directly or using proxies, to undermine our national security and our democracies.

The UK and France are willing and able to act together, decisively, to protect our shared interests, allies, partners in Europe and beyond, values and, fundamentally, our democratic way of life. We must be ready and willing to oppose our adversaries across the full spectrum of national security, requiring a new, whole of society and government approach. We are resolved to deepen and expand our partnership to jointly deter and respond to the heightened challenge these evolving threats pose including cyber, sabotage, espionage, malign use of artificial intelligence and foreign information manipulation and interference. This can only be achieved by the further integration of our Military, National Security, Diplomatic, Intelligence and Economic levers.

It is in this context that we, as Prime Minister of the United Kingdom of Great Britain and Northern Ireland and President of the French Republic, have decided to reboot, modernise and build upon our bilateral defence and security relationship, including under the Lancaster House Treaties, in order to effect a generational shift in both our bilateral cooperation and our joint contribution to the defence of Europe, its citizens and of its interests. Today, we have declared our intent to carry out a series of ambitious projects and new areas of collaboration that will underpin our defence and security relationship for the next fifteen years and beyond.

1. Deepening our longstanding and resolute commitment to cooperation between our independent nuclear deterrents by:

a. Setting out our contribution to the defence of European partners and NATO Allies, and stating that whilst our nuclear forces are independent, they can be coordinated, as set out in the Northwood Declaration;

b. Enhancing mutual understanding of respective nuclear deterrence policies, doctrine and plans, and strengthening our ability to make coordinated decisions in peace time and in crisis;

c. Expanding cooperation on nuclear research (as initiated since 2010) including by making greater use of the facilities in each other’s countries;

d. Coordinating more closely to uphold and reinforce the international non-proliferation architecture; and

e. Establishing a UK-France Nuclear Steering Group to provide political direction for this cooperation, led by the Presidency of the French Republic and the Cabinet Office to coordinate across policy, capability and operations.

2. Launch the Combined Joint Force – overhauling the existing Combined Joint Expeditionary Force to refocus it on the Euro-Atlantic and warfighting at scale to deter, placing it on an operational footing for the first time by endeavouring to:

a. Significantly increase the declared Combined Joint Force (CJF) capacity, up to fivefold, ensuring the ability to plan and command Combined Corps Capability (the highest level of fielded forces in our armies). This Corp can provide the Land component of a broader joint force combining all military functions, as part of NATO or bilaterally. The CJF will facilitate the deployment of a force fully interoperable with NATO and available as the Alliance’s Strategic Reserve; this is a critical step towards the UK and France providing two fully interoperable Strategic Reserve Corps to NATO, enabled by the CJF.

b. Adopt new missions, enabling the CJF to conduct activity in the Euro-Atlantic to deter our adversaries and reassure our Allies and partners, while also being prepared to compete with our adversaries further afield if needed.

c. Establish a mechanism to share, coordinate and synchronise military activity and the deployment of UK and French forces globally, ensuring we are providing the most effective deterrence posture.

d. Establish a dedicated cell to operationalise the CJF, overseeing military strategic coordination and planning through to operational coordination.

e. Maintain the ability for the CJF to integrate additional allies and partners under UK-French leadership and to ensure the CJF is complementary to NATO.

f. Use the CJF structures to underpin the Coalition of the Willing for Ukraine. The force will provide the joint planning framework to cohere the Coalition, ensure joint operational and strategic messaging. It will provide Coalition leadership and command and control for the planning and operational deployment of the Coalition covering all five domains, preparing for the operational deployment of the CJF in the event of a ceasefire – which can be supported by allies.

3. Embark upon an ‘Entente Industrielle’ to enhance capability and industrial co-operation, bringing our defence industries and militaries closer than ever before to strengthen NATO, by endeavouring to:

a. Launch the development phase of the Future Cruise and Anti-Ship Weapon (FC/ASW) programme to provide the next generation of long-range, highly survivable Deep Strike Missiles.

b. Jointly develop the next generation of beyond-visual-range air-to-air missiles for our fighter jets, while also extending the Meteor capability, launching a joint study with industry to inform our future development of its successor.

c. Acquire new SCALP & Storm Shadow missiles, following their successful use by Ukraine, upgrading UK and French production lines to bolster national stockpiles to deter our adversaries.

d. Establish a new, joint Complex Weapons Portfolio Office, embedded with OCCAR, through which we will deliver our joint projects within OCCAR, starting with SCALP & Storm Shadow acquisition and also working closely with MBDA to identify the opportunities from our investments and to reduce duplication, working closely with MBDA, starting with studies on Air Dominance and Cooperative Strike future capabilities.

e. Focus greater efforts on integrated air and missile defence (IAMD) in our capability relationship, including (but not limited to) C-UAS and counter-hypersonic capabilities, drawing especially from the Aster family increments, including potentially SAMP/T NG and CAMM.

f. Continue to work closely on current and future long range strike capabilities through the European Long Range Strike Approach (ELSA initiative). Along with our ELSA allies (amongst them Germany), we will remain open to expanding this cooperation to extended-range deep strike capability should military requirements and industrial capacity align. We will be carefully examining, with our defence industries, the capability opportunities this presents.

g Develop a Directed Energy Weapons partnership, sharing information, collaborating on research and projects of shared interest, and exploring industry collaboration on radiofrequency weapons.

h. Collaborate on developing algorithms for synchronised missile and drone strikes using artificial intelligence and machine learning, to build our future interoperability.

i. Explore a combat air interoperability roadmap, including potential collaboration on armaments, to support the connectivity and interoperability of our current and future combat air forces and their contribution to European and NATO air superiority.

j. Commit to align standards for weapons safety and testing, to bring operational benefits and save time and money in our joint programmes.

k. Work closely together on wider export campaigns for UK-French capabilities and establishing a new joint team, with an initial focus on supporting the export of A400M (including through the set up of a NATO High Visibility Project) and identifying further concrete areas for joint export promotion.

l. Recognising the importance of improving European defence industrial resilience, the UK and France will enhance reciprocal market access in defence and security.

4. Develop new cooperation in every domain to enhance military interoperability and support NATO, driven by annual meetings of our Joint Chiefs. This will include:

a. Developing a new Bilateral Vision Statement between the armies and committing to enduring support to NATO through the CJF. This represents operational interoperability at the highest level of fielded forces in our armies, enhancing British and French joint commitments and opportunities offered through the Forward Land Forces in Estonia.

b. Driving naval interoperability in support of warfighting, notably on information, data and communications, leveraging the opportunities of next generation digital architectures, deepening cooperation on maritime air defence, and continuing to coordinate Carrier Strike Group activity. Additionally, expanding cooperation on global maritime domain awareness to better deter maritime hybrid threats, including to critical undersea infrastructure and sanctions circumvention by the Russian Shadow Fleet, with an initial focus on the Channel and the Atlantic. Finally, facilitating mutual access support facilities for naval aircraft and warships.

c. Increasing the complexity of combined Air Defence exercises, cooperating on responses to High-Altitude threats, enhancing cooperation in the development of Counter-Unmanned Aerial Systems (C-UAS) capabilities, particularly in the integration of Command And Control (C2) systems. Pursuing a joint ambition to develop the A400M into a multi-mission platform, incorporating C2, Intelligence, Surveillance and Reconnaissance (ISR) and potential strike capabilities. Aiming to synchronise fast jet pilot training to enhance interoperability and efficiency.

d. Enabling interoperability across the space domain, including satellite communications capabilities, developing cooperation and potential joint capability in space control, space-based ISR systems, and Low Earth Orbit satellites. We will jointly spearhead closer operational space coordination and deliver space support to bolster Euro-Atlantic security operations.

e. Sharing best practice in Cyber, with the UK providing support to the French establishment of a Cyber Training Academy, and France supporting the establishment of the UK’s new Cyber & Electromagnetic Command. Jointly galvanising wider NATO Cyber exercise activity, whilst fusing UK-French operational cooperation to act amongst Allies as European leaders in the domain.

5. Reinforce the UK-France integrated defence and security partnership to deter and respond to the full spectrum of threats, by endeavouring to:

a. Work together to make the fullest possible use of the UK-EU Security and Defence Partnership. Noting the shared UK and EU commitment to explore possible mutual involvement in respective defence initiatives, including within the Security Action For Europe (SAFE) instrument, in accordance with the respective legal frameworks, the UK and France will explore possibilities for mutually beneficial enhanced cooperation.

b. Strengthen our defence and security policy coordination and cooperation on key areas for Euro-Atlantic security (Ukraine, NATO, the future of Euro-Atlantic security) and reasserting the unique contribution of our bilateral partnership to European and global security.

c. Exploit areas of policy dialogue and cooperation in countering hybrid threats, Space, Cyber and AI – including through fostering links between national agencies, exchanging doctrines and responsible practices.

d. Launch a new Global Maritime Security Dialogue to cohere our strategic approaches to deterring threats to our shared maritime interests.

e. Establishing a dialogue on Humanitarian Assistance and Disaster Relief to build on our existing frameworks and scope future mutual assistance arrangements.

f. Coordinate and align resources to enhance regional resilience, including on maritime security, in the Indo-Pacific in the medium-term and, in accordance with our respective international obligations, provide for reciprocal base access to facilities, including Réunion Island, New Caledonia and French Polynesia.

g. Bring together our intelligence, law enforcement and policy expertise across the overt and covert environments to deter, counter and respond to the full range of hybrid threats including physical threats to people, sabotage and foreign interference, including Foreign Information Manipulation and Interference (FIMI), cyber and espionage. Jointly pursuing attributions and coordinating on sanctions, as well as exploring how we can further lead joint operational efforts to combat the hybrid threats. We will continue our cooperation in NATO, G7 and other multilateral forums.

h. Further strengthen our cooperation to counter FIMI, to raise the costs for states seeking to undermine our security and democratic institutions. We will pursue the interoperability of our systems to analyse FIMI and increase efforts to jointly respond to it, including through exposure, sanctions and strategic communication. We will continue working together to build collective responses to FIMI in multilateral fora.

i. Build on the UK-French Pall Mall Process and the Paris Call for Trust and Security in Cyberspace, to tackle the threat posed by the proliferation of commercial cyber intrusion capabilities and address the shared challenges we face in cyberspace, and increase the cost to our adversaries through deterrence, sanctions and attributions.

j. Engage in regular technical exchanges and proactively exploring joint research opportunities to harness the transformative potential of Artificial Intelligence and emerging technologies, while addressing associated national security challenges. The UK and France are uniquely placed to lead international efforts and response capabilities.

k. Jointly maximise our impact against the highest-threat terrorist groups. Internationally, we will deepen our cooperation with Syria, and will look to enhance our coordination against the expanding terrorist threat in sub-Saharan Africa and central Asia. Domestically, we will build resilience against terrorist threats to critical infrastructure, including transport connections between our countries.

6. Enhance communications and institutional exchanges across our two systems, as an enabler to our strengthened partnership across the entirety of defence and national security, by endeavouring to:

a. Develop a new joint UK-France cross government secure communication system.

b. Expand people and training links between the UK and French Militaries, optimising our networks of exchange and liaison officers, with a focus on junior officer exchanges, to develop a shared strategic culture in the next generation of military leaders across all three services.

c. Continue to enable the constant exchange of national security and defence personnel and their families, to constantly deepen and forge our relationship for future generations and to ensure our Armed Forces have the conditions they need to perform effectively, and that they, and their family members, do not experience disadvantages as a result of their service. This might include reciprocal access to rights to work and related facilitations for defence personnel and their household members serving in each other’s countries.