Maximising UK-German Defence and Security

The deterioration of European security since the start of Russia's 2022 war on Ukraine has driven the recent strengthening of defence and security cooperation between the UK and Germany. However, the second Trump presidency is arguably more challenging as the primary source of instability is the commander-in-chief of their mutual pre-eminent ally, not the aggression of their principal foe. As the two largest European defence spenders in NATO and the top two European supporters of Ukraine in absolute financial terms, the UK and Germany will have to shoulder far more of the European security burden. They must do this together.

On 28 August 2024, the prime minister and chancellor announced that a new bilateral cooperation treaty would be negotiated by their respective foreign ministries. On 23 October 2024, the UK and German defence ministers signed the 'Trinity House Agreement', which has established defence cooperation as a key pillar of this new Treaty-based relationship. The Treaty will include several additional policy areas, including foreign policy, justice and law enforcement, economic growth, resilience, science and technology, energy and climate, and the environment. There is broad cross-party support in both countries for the Treaty and it is likely that it will be signed soon after the new German government takes office on 6 May 2025.

This Policy Brief examines how the UK and Germany can maximise the new relationship to ensure that it delivers the most value to each of them and to European security. The brief argues that the political desire to broaden the UK–German relationship across multiple policy areas simultaneously poses a risk to delivering on progress made in defence and security cooperation. The rapid deterioration of Euro-Atlantic security as a result of Trump's early rapprochement with Russia – at the expense of Ukrainian security – will immediately stress-test the new relationship and there will be pressure to deliver immediate value. Consequently, the Treaty must focus on building mutual political commitment and creating effective governance structures, so that the strategic partnership becomes more than the sum of improved cooperation between Whitehall departments and their respective German federal ministries.

The research for this brief is drawn from two main sources. First, a review of official UK, German, NATO and EU policy documents, alongside expert and media commentaries. Second, an expert-led roundtable discussion – held in London on 25 November 2024 – which was attended by a member of the German Bundestag, academics, and representatives from the UK Foreign, Commonwealth and Development Office and the German Embassy in London. The brief is supported by Konrad Adenauer Stiftung's London office.

This brief is structured in three sections. The first section assesses the intensification of the relationship since the Labour government took office. The second explores the shared political opportunities and risks and the third focuses on developing coherence through strong governance structures. The conclusion identifies the priorities for establishing a value-based relationship.

On 23 October 2024, the defence ministers of the UK and Germany signed the 'Trinity House' defence agreement. Signed just 111 days after the Labour government was elected, the agreement covers strengthening defence industries, reinforcing Euro-Atlantic security, enhancing interoperability, addressing emerging threats, supporting Ukraine, and working together on future ‘Deep Precision Strike’ capabilities. Moreover, the defence agreement created several 'lighthouse projects', including German maritime patrol aircraft operating from RAF Lossiemouth, and established new governance structures to accelerate delivery. Demonstrating the centrality of the defence partnership, a German military planner is currently embedded in the UK Strategic Defence Review team.

As Claudia Major and Nicolai von Ondarza concluded, it is 'politically noteworthy' that 'Labour has chosen security and defence as the main angle for their “reset” with European allies and the EU'. Therefore, the significance of Trinity House goes beyond a bilateral defence agreement and should be considered as both a framework and a model for closer UK cooperation with Europe and the EU. However, in the haste to finalise the agreement, two important elements were omitted.

First, export controls – a previous point of friction – were absent. Joint capability development proposals under Trinity House, especially Deep Precision Strike, will have significant export potential with Ukraine, exposing Russia’s vulnerability to such systems. An agreement on export controls will be crucial for building confidence and maximising the benefits from future joint procurement opportunities. Export controls are not led by the defence ministries in either country and will therefore need more political focus from ministers responsible for trade and industry, requiring greater political trade-offs to gain alignment.

Second, since the agreement was signed, both countries have strengthened their respective defence industries. Germany has published its National Security and Defence Industry Strategy and the UK has announced a new Defence Industrial Strategy to be published in the spring. The UK wants to use defence (as one of eight priority sectors) to pursue growth and prosperity by onshoring a higher proportion of defence industrial capacity, whereas Germany is focusing more on pan-European cooperation. The external situation has also changed, as the US acts more unpredictably and raises concerns in Europe about overdependence on the US and buying American manufactured arms covered by the International Traffic in Arms Regulations (ITAR) in the future. This stands alongside strained transatlantic relations over trade tariffs. As both the UK and Germany buy a significant amount of US equipment, this shift will be a strategic challenge jointly felt by both parties.

However, the situation is also an opportunity to strengthen UK–German and European joint procurement, especially as the EU adopts its €800-billion ReArm Europe defence package. Creating closer alignment between UK and German industrial strategies would be a quick win and an effective precursor to UK–EU defence industrial collaboration to hedge against the unpredictability of the US. Moreover, the UK should immediately lobby the new government in Berlin to help gain access to the new EU €150bn rearmament fund ahead of the UK–EU summit on 19 May 2025, where an agreement on defence and security is expected.

Although defence cooperation is most advanced, economic growth and illegal migration are both higher joint domestic joint political priorities. Keir Starmer has made ‘economic stability’ and ‘secure borders’ (alongside national security) the 'foundations' for his 'Plan for Change' and mission-led government.

'Strengthening our relationship with these countries (Germany and France) is crucial, not only in tackling the global problem of illegal migration, but also in boosting economic growth across the continent and crucially in the UK – one of the key missions of my government,' he said during the announcement of the bilateral treaty negotiations.

The political imperative to boost mutual economic growth is stark. Germany is the UK’s second-largest trading partner, accounting for 8.5% of UK trade. The German government has struggled to pass federal budgets, limited by the 'debt brake', leading to a loss of confidence in economic stability and responsibility – a traditional German strength – and also leading to calls for major fiscal and economic reform to stimulate growth. The fiscal necessity has already driven significant reform ahead of the new government taking office as, on 18 March 2025, the Bundestag voted to exempt defence spending from Germany's strict debt rules and create a €500-billion infrastructure fund. Simultaneous political deadlock in France has slowed the Franco-German economic and integration motor at the heart of the EU, with confidence in the traditional leaders diminishing. Furthermore, the economic outlook could worsen as a looming tariff and trade war between the US and China will also negatively impact the EU. Starmer has already rejected making a binary choice between closer ties with the EU or US, but that was before Trump’s imposition of global tariffs and the leaked Signal discussion between key national security members of the US administration that made their feelings towards Europe well known. In this more challenging situation, closer alignment with key economic players in Europe will benefit the UK.

Similarly, immigration is high on the political agenda. It is also a clear area of cooperation, as the governing parties are challenged by anti-migration parties. However, neither are priority partners for addressing illegal immigration: with the UK prioritising working with France, and Germany addressing southern migration with Italy and Greece. Therefore, explicitly highlighting closer working could create unrealistic expectations of delivery. In the UK, Reform has gained 12 percentage points as of March 2025, since the 2024 general election, putting them ahead of Labour for the first time. Meanwhile, the Alternative for Deutschland (AfD) – which based its electoral campaign on immigration rhetoric – became the second-largest parliamentary group after securing 20.8% in the federal election. Both the Christian Democratic Union (CDU) and the AfD took strong anti-immigration stances which clearly contributed to their electoral success.

On 10 December 2024, the UK Home Office and the German Federal Ministry of the Interior and Community set out a 'Joint Action Plan on Irregular Migration’ agreement to target small boat crossings. The plan commits Germany to clarifying its law to make it a specific criminal offence to facilitate the smuggling of migrants – many boats are procured in Germany – and aims to make it harder to cross the English Channel. Moreover, it welcomes more involvement from Europol, which will likely feature prominently in a future UK–EU security deal.

Economic growth and immigration control can be domestically politically volatile. Public disagreements between the UK and German governments on immigration could easily derail greater cooperation on defence and security, or wider UK–EU cooperation, as difficulties in one policy area could easily impact the other. This makes insulating defence and security from the political weather more important. Finally, each government might also find it difficult to directly attribute successes on growth and migration to these agreements. To mitigate these risks, the UK and Germany should design effective governance structures.

Expanding the policy areas for a Treaty to manage risks the UK–German relationship becoming imprecise and unwieldy, which only achieves better department-to-ministry cooperation but fails to deliver a coherent strategic partnership. Adding additional policy areas means that cooperation could touch as many as 13 of the 34 UK ministerial departments and 10 of 15 German federal ministries (including the Office of the Prime Minister and the Federal Ministry of the Chancellery) and more non-ministerial departments, agencies and public bodies. The UK and Germany should learn from their 2021 Joint Declaration, which covered a vast range of policy areas and global regions, and was too unwieldy for the foreign secretaries to deliver.

Designing and implementing an effective governance structure could mitigate this risk and is an opportunity to consolidate and streamline legacy arrangements. This governance structure should focus on three key objectives: maximising political direction and buy-in, reducing duplication and intensifying integration.

First, the structure should maximise political direction and buy-in. The prime minister and chancellor must be directly involved to ensure high-level political attention, to maintain momentum, to hold ministers to account and ensure delivery of the full agenda, through regular consultations and joint Cabinet meetings. While Trinity House – both the agreement and the speed at which it was signed – was a Labour-SPD social democratic deal, it is important that better political linkages are now made with Labour and the CDU. To build cross-party consensus, parliamentary dialogues should increase and move away from organising on party political lines.

Second, the structure should reduce duplication. Ministerial diaries are already too demanding, and more bilateral minister-to-minister interactions within each policy area could become cumbersome. Instead, it would be beneficial to open the extant strategic dialogue between foreign ministers (established in the 2021 Joint Declaration) to also include defence and home secretaries, to have a more comprehensive security focus. Opening dialogues between foreign, defence and home secretaries would enable greater political interest, accountability and the ability to develop integrated policy responses to complex security challenges. However, the substance of the discussions must make these more substantial dialogues worthy of ministers’ time.

Third, the structure should intensify UK–Germany integration. Both the UK and Germany operate an integrated approach to security and some functional areas – for example, intelligence cooperation – sit across multiple ministerial departments. The range of conventional and hybrid threats both countries face, from foreign election interference to incendiary DHL Parcels, and Russian military aggression against the Baltics (where the UK and Germany lead NATO’s Forward Land Forces), requires greater integration across departments and their associated agencies. The new CDU Chancellor Friedrich Merz wants to revisit the establishment of a German National Security Council (NSC) within the Chancellery after the previous coalition was unable to agree on such a machinery of government change. Creating a German NSC would establish a new and important link between UK and German national security advisers, which could foster greater integrated intelligence cooperation. Intelligence cooperation is currently underused – it was not covered in Trinity House – and falls between the seams of foreign, defence and security policy. Moreover, the UK has operated a NSC for 15 years, which has undertaken multiple reforms to remain valuable and can offer advice to Germany on establishing the office (given previous difficulties in agreeing how it would operate and where it would best be housed).

Externally, the new bilateral Treaty will impact other European relationships, which will need managing, and which are working in overdrive since Trump’s re-election. These include the E3 (the UK, Germany and France), the Weimar Triangle (Germany, France and Poland), the ‘Weimar Plus’ (Poland, Germany, France, Italy, Spain, the UK and the EU’s High Representative for Foreign and Security Policy) and the newer E5 format (the UK, Germany, France, Poland and Italy). Within this system there is too much duplication, and each meeting must add value in a fast-paced environment. The UK and Germany are common denominators in many of these formats and by working together and harnessing the momentum of the bilateral they could level up these formats and revitalise them. As European defence and security leaders, they should combine their influence to prioritise and focus energy into progressing policy within one strong group. Bringing the E3 together with the Weimar Triangle would develop the strongest new European quad of powers, which could jointly lead in the absence of the US on European security and bridge NATO and the EU.

Stronger government-to-government relationships should be reinforced by sharpening non-governmental structures which advocate for closer ties across foreign policy, economics, education, cultural exchanges and youth groups. Some groups are specifically referenced by the 2021 Joint Declaration as ‘key fora for outreach and feedback, and an opportunity to maintain a strong and close relationship’. Therefore, there is no need to establish new structures. Rather, more impetus should be placed into breathing new life into the existing ones. As examples, the annual Königswinter Conference, and its Defence counterpart, have been operating yearly since 1950 and 2010, respectively, and the British-German Association since 1951. Multiple attendees have expressed a view that these groups have become stale, procedural and have not kept pace with changes in policy.1.  These groups should be reinvigorated, through revitalising the attendees, securing fresh partnerships, and inviting them to establish working groups which match the areas for further UK–German policy development. Moreover, German Stiftungen (political foundations) are a key advocacy group for closer cooperation and should be allowed to operate on a more substantial footing.

The 2021 Joint Declaration was an important starting point for rapprochement after Brexit, but it was not legally binding. Therefore, the Treaty has the opportunity to develop stronger political buy-in and form a joint agenda on strengthening European security. Merz reportedly has an affinity with the UK and his campaign commitments and public announcements align closely with UK defence and security objectives. There are three priorities to seek alignment on: creating a strong leadership bond and mutual leadership positions in NATO; sustaining Ukraine’s defence; and elaborating a unified European position on China.

First, UK and German objectives within NATO align closely as committed Atlanticists and they will be particularly vulnerable to significant US changes in policy towards Europe. The UK and Germany will need to fundamentally re-evaluate their defence and security approaches and doctrines, which have been developed over decades. Therefore, the Treaty must hedge against this and create a strong leadership bond at the heart of NATO that can best address the threat posed by Russia. Increasing their mutual leadership positions in NATO could also help to keep NATO in as close to its current form as possible, in the face of changing US policy towards the Alliance, which is a joint strategic interest.

The June 2025 Hague Summit is the most immediate challenge. As the top two European defence spenders, creating a harmonious position will be critical, especially as Germany is the target of Trump’s frustrations with European allies – despite currently being the second-highest spender in NATO, after decades of underspending relative to its economic size (and with questions remaining about the sustainability of its defence spending increase). Trump wants Europeans to spend 5% of GDP on defence. While such a figure is unrealistic, it creates certain US expectations. Pre-empting the debate, in his first major speech the new NATO Secretary General Mark Rutte said ‘to prevent war, NATO must spend more’ and believes the NATO target should be raised from 2% to 3%.

Second, sustaining Ukraine’s defence should be a priority. As an immediate win, Merz has personally committed to supplying Ukraine with long-range Taurus missiles – which Chancellor Scholz has repeatedly refused to do – and will likely seek US and French support. Delivering such a system to Ukraine would bring Germany in line with the UK, France and the US in the provision of long-range strike assets.

The more immediate and risky challenge is the potential deployment of European reassurance forces in Ukraine to secure any negotiated ceasefire. Thus far, the UK and France have taken the lead in assembling a potential 30-strong coalition of the willing that could deploy to Ukraine in the right circumstances. German officials have also worked with their UK and French counterparts to help the US and Ukraine reach a ceasefire deal which can be presented to Russia.

This presents both a dilemma and opportunity for the new German government. Chancellor Scholz had ruled it out, only for his foreign minister to suggest it might be necessary. Therefore, Germany might be pressured into an early decision on the deployment of German troops outside NATO borders, which has traditionally been politically sensitive, and must be supported by both the UK and France. However, it would also be an opportunity to show that Germany is ready to step up and lead on European security and that the Zeitenwende is not just about more money for the Bundeswehr, but also a mindset change in the deployment and employment of military force.

Third, Trump is expected to focus on China, making it more important for a unified European position. Last year, the German government published a Strategy on China which states that ‘China is simultaneously a partner, competitor and systemic rival for the Federal Government. Our Strategy on China is firmly rooted in the common policy on China of the EU’. Derisking and diversification rather than economic decoupling became the policy, but with derisking left as an individual business decision, rather than a Federal diktat. The UK government is currently undertaking a ‘China audit’. The 2023 Integrated Review Refresh defined China as an ‘epoch-defining and systemic challenge’. The extant ‘3Cs’ China policy approach of ‘compete, challenge, and cooperate’ is similar to the simultaneous and overlapping German positions. Moreover, the new UK government has already changed its approach to get closer to China on trade, which is also closer to the current German position. As both governments seek to balance trade and security in their individual and collective approaches to China, cooperation is important. Furthermore, while these policies are being developed, external factors will also shape what is possible – NATO explicitly called out China as a ‘decisive enabler of Russia’s war against Ukraine through its so-called “no limits” partnership’ at the NATO 2024 Washington Summit. Trump is also likely to apply pressure to allies who strengthen their economic links with China.

The Treaty will elevate the relationship and will be binding under law – going beyond the Trinity House Agreement. But the Treaty itself will not deliver the value required. Rather, the mutual political buy-in to the relationship, along with the shared challenges that the UK and Germany will face in the future, will.

The UK–German bilateral relationship will be maximised in the context of the broader UK–EU relationship. The Labour government has stated that ‘The new UK-Germany treaty will be a key pillar of the UK’s wider reset with Europe’. Some analysts have calculated that a successful ‘reset’ with the EU could raise UK GDP by 0.3–0.7% and the German relationship will be integral to achieving this. However, Brussels is likely to want movement on fisheries and a youth mobility scheme in return for a defence and security deal. Through improving relations with Germany – a central EU power – the UK has put itself in a stronger negotiating position. However, the UK must be realistic and accept that while this might support future negotiations with the EU, it will be no panacea, and these negotiations are likely to be challenging and could strain growing UK–German cooperation.

The UK and Germany – individually and collectively – will be severely impacted by external shocks across most policy areas. Both also have growing internal challenges. The new UK government is already realising how difficult it is to govern, even with a large majority. The new German government might not have the strength to lead Europe and will need to rely on partnerships with other countries. Domestic political considerations on the economy and immigration, coupled with the challenge of populist parties, will take priority, even as international security problems mount.

With reduced US leadership in Europe, no one country can fill the vacuum. However, a group of leading European countries – including the UK and Germany – can mitigate this to a certain degree and keep European security together in something close to its current form. By increasing bilateral partnerships, the UK and Germany can be in the best position to shape the future to their advantage and set UK–EU relations on the right path. Here, the real value is less about what is written within the various agreements and communiqués that govern the partnership, but rather how they are used, developed and driven by political leaders on both sides, regardless of the parties to which they belong.