International security cooperation is undergoing a profound transformation. Institutions that once structured collective responses to crises are increasingly constrained by geopolitical rivalry, declining effectiveness and growing legitimacy challenges. The NAVIGATOR working paper The end of multilateralism as we know it? Assessing current trends in international security examines how security governance is evolving and what this changing landscape means for the European Union.

Rather than signalling the disappearance of multilateralism, the paper shows how security cooperation is being reconfigured. Formal organisations remain central, but they now coexist with more flexible and state-driven arrangements that reshape how collective action is organised.

A shifting environment for global security governance

The rules-based international order that has long underpinned European security policy is under pressure. Intensifying great power competition, Russia’s invasion of Ukraine and growing geopolitical polarisation have narrowed the space for cooperation in many established forums. At the same time, scepticism about the capacity of existing institutions to deliver tangible security outcomes has become more widespread.

For the EU, this context is particularly challenging. As a long-standing supporter of institutionalised and rules-based cooperation, the Union is now operating in an environment in which security governance is becoming more transactional, selective and politically contested. The paper highlights three overarching pressures shaping this evolution: geopolitical rivalry, declining institutional effectiveness and a growing crisis of legitimacy.

From institutional gridlock to flexible security arrangements

One of the paper’s central observations is the increasing reliance on informal and task-oriented formats of cooperation. When formal organisations face political deadlock or operational constraints, states increasingly turn to ad hoc coalitions in order to act more rapidly and retain tighter control over decision-making.

These coalitions are usually temporary, flexible in membership and focused on concrete operational objectives. They are becoming an important feature of contemporary security governance, especially in crisis response and military cooperation. The EU has actively contributed to this shift, notably through the European Peace Facility, which has enabled direct support to partners and coalitions in contexts such as Ukraine and counter-terrorism operations in Africa.

While these arrangements offer speed and operational flexibility, the paper underlines that their growing prominence also raises governance concerns. Ad hoc coalitions do not provide the same institutionalised oversight, long-term commitments and normative frameworks as formal organisations. Over time, a strong dependence on such formats risks weakening the institutional structures that underpin predictable and legitimate security cooperation.

Formal organisations under strain

The paper examines how key international and regional organisations are adapting to this changing environment, with a particular focus on the United Nations Security Council and UN peace operations, the African Union, the OSCE and NATO.

At the global level, the UN Security Council remains the main forum for international peace and security. However, its capacity to respond to major crises is increasingly constrained by veto use and political polarisation. At the same time, the drawdown of UN peace operations and the absence of new large-scale missions reflect both geopolitical divisions and growing doubts about the effectiveness of traditional peacekeeping instruments.

In Africa, the African Union continues to play an important normative and political role, supported for many years by the EU. Yet regional security cooperation has become more fragmented, with sub-regional operations and ad hoc coalitions often replacing established mechanisms. Coups, shifting alliances and external involvement have further complicated the institutional environment.

The OSCE illustrates a different type of institutional pressure. Although its consensus-based decision-making has become a significant limitation in the current political climate, it remains one of the few pan-European platforms in which dialogue between Russia and Western states still takes place.

NATO has meanwhile re-centred its mission on territorial defence and deterrence following the war in Ukraine and the rise of hybrid threats. At the same time, uncertainty surrounding long-term US engagement and burden-sharing has increased pressure on European allies to strengthen their own defence capabilities and deepen cooperation.

The EU between geopolitics, effectiveness and legitimacy

Across these institutional settings, the paper identifies a fundamental dilemma for the EU. A more geopolitical approach may strengthen the Union’s ability to protect its interests and respond quickly to crises. However, this can come at the expense of inclusiveness and the legitimacy of global and regional institutions that the EU has traditionally supported.

Efforts to increase effectiveness through flexible and informal cooperation can generate short-term operational gains, but they also risk reinforcing perceptions of selective multilateralism and weakening support for universal institutions. At the same time, demands for more inclusive global governance, particularly from emerging and developing countries, challenge existing power distributions and may reduce the EU’s relative influence.

The paper argues that no single institutional arrangement can resolve these tensions. Instead, the EU must continuously navigate trade-offs between geopolitical relevance, institutional effectiveness and normative credibility.

Towards a more strategic use of security institutions

Looking ahead, the paper suggests that the central challenge is not whether formal organisations or ad hoc coalitions should dominate security cooperation, but how different instruments can be combined more strategically.

Ad hoc coalitions can play a useful role when formal institutions are blocked or slow to respond. However, they should be designed in ways that complement established organisations rather than compete with them. Political endorsement by relevant regional and global institutions, clearer functional differentiation and stronger coordination are essential to prevent further institutional erosion.

In an increasingly crowded and fragmented security governance landscape, the EU’s influence will depend less on the creation of new formats and more on its capacity to organise cooperation across multiple institutional layers. Using different arrangements for different purposes, while preserving the legitimacy and long-term capacity of formal organisations, emerges as a key principle for navigating security cooperation in a crisis-driven multilateral system.