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Good to Know: Collective security

An explainer on collective security agreements like NATO.

- January 9, 2024

For NATO, the North Atlantic Treaty Organization, 2024 got off to a busy start. In February, Hungary’s parliament approved Sweden’s membership bid, clearing the way for the once-neutral country to join the alliance. Sweden and Finland both applied to join NATO after Russia invaded Ukraine in 2022. Russia’s response to Sweden’s progress towards joining the alliance included a pledge to take “retaliatory steps of a military-technical and other nature” to counter NATO’s expansion.

NATO also has deepened relations outside of its membership this year. French President Emmanuel Macron suggested in February that the alliance could send troops to Ukraine, saying, “Nothing should be excluded. We will do everything that we must so that Russia does not win.” NATO’s leadership quickly denied it planned to send forces to Ukraine, which is not a NATO member, while still pledging material support in its fight against Russia. In response, Russian President Vladimir Putin warned of dire consequences if NATO troops directly intervened in the ground war.

And NATO continues to strengthen military ties with non-member countries. NATO’s Joint Force Commands held a training exercise in Moldova. Such joint exercises are standard, and Moldova has been a member of Partnership for Peace since 1994. But the training exercise comes at a particularly tense moment, as pro-Russian forces in Moldova appeal to Russia for “protection” in the breakaway region of Transnistria. 

NATO has a 75-year history

All of this raises questions about the future of NATO as a collective security organization in an age of intensifying great power competition and conflict. Founded in 1949, the organization originally included 12 members. With Finland and Sweden’s accession, NATO now has 32 members, including countries on Russia’s borders. 

Since the end of the Cold War, NATO’s numbers have expanded, along with its mission. Originally formed to deter Soviet aggression, in the 1990s NATO intervened to stop ethnic conflict in the Balkans. After 9/11, the alliance reoriented its focus towards counterterrorism and counterinsurgency operations. Russian aggression in Ukraine has only increased support for the alliance, both among elites in member countries and the public at large.

What is collective security?

When countries engage in “collective security,” they agree to act as a unit to defend any member who is a victim of attack. Collective security agreements may have limited and exclusive membership, as is the case with the North Atlantic Treaty Organization. Other collective security organizations – the League of Nations after World War I, or the United Nations Security Council today – aspire towards a more universal concept of collective security, and are theoretically open to all countries.

At the heart of collective security arrangements is the members’ commitment to respond to aggression. For example, article 5 of the NATO charter declares that any attack against a NATO ally “shall be considered an attack against them all.” In response, NATO members will defend their ally, with actions it “deems necessary, including the use of armed force, to restore and maintain the security of the North Atlantic area.” Chapter 7 of the U.N. Charter instructs the U.N. Security Council to act in the face of aggression, deciding “what measures shall be taken in accordance with Articles 41 and 42, to maintain or restore international peace and security.”

Do collective security institutions help peace?

Political scientists disagree about whether the persistence of these institutions matters for international relations. Realist scholars argue that countries necessarily look out for themselves, not others, and are more likely to compete than cooperate in world politics. For that reason, collective security institutions do little if anything to shape a country’s foreign policy. Yes, countries will promise to engage in collective defense – when they feel threatened. NATO’s formation in 1949 was a response to an ever more threatening Soviet Union, just as NATO’s recent rejuvenation was a response to Russian aggression. At most, these scholars believe, collective security institutions can enhance their members’ joint fighting capacity. These institutions cannot force countries to take on aggression if it is not in their interest.

For liberal and constructivist scholars, in contrast, collective security institutions are an essential part of the norms and rules of international order – and thus help keep the peace. One way is by demonstrating a commitment to multilateral action, a key pillar of liberal world politics. Another is by bringing together countries with shared values and deepening cooperation between them. This process shapes the rules of international relations, such as the norm against aggression.

Is collective security endangered?

In fact, 2024 is likely to be a critical moment for collective security organizations. NATO seems more resilient than at any moment since the end of the Cold War. After the tumult of the presidency of Donald Trump, who consistently derided the organization for free-riding off the United States, the Biden administration has pledged a continued U.S. commitment to the alliance. And in wake of Russia’s 2022 invasion of Ukraine, NATO exhibited its capacity to act with shared purpose in the face of aggression – and even welcomed two new members, Finland and Sweden.

Yet troubled days lie ahead. The U.N. Security Council has struggled to act collectively in conflicts in Ukraine and Gaza. Permanent Security Council members have used their veto power to stymie even modest ceasefire proposals. Despite NATO’s resurgence, the organization is still managing squabbles amongst its members over support for Ukraine. In February 2024, for instance, other NATO members were quick to distance themselves from Macron’s remarks. 

And if Trump wins the November 2024 presidential election, U.S. commitment to collective security becomes uncertain at best. Trump’s threats to let Russia do “whatever the hell they want” to NATO allies who fail to raise defense spending are a stark reminder that U.S. support of the alliance is not guaranteed. The U.S. election aside, 2024 is likely to bring continued strain on collective security institutions, be it from intractable conflicts, increased great power competition, or from fighting inside the alliance itself.

What would the decline of collective security mean?

Collective security institutions are in for a rough ride – few would dispute that outlook. But theories of international relations point to different implications if collective security falters. Realists, who never thought collective security mattered much, would likewise expect little to change. 

Liberal and constructivist scholars, in contrast, see recent trends as a disturbing harbinger, not only for specific institutions, but for the future of international politics as a whole. Struggles in collective security institutions represent the breakdown of norms and rules undergirding the current international order. Ineffective collective security institutions, thus, would undermine the commitment to multilateral action, place strains on norms against aggression, and weaken countries’ resolve to protect territorial integrity. At the extreme, tensions within NATO could signal the demise of the commitment of democracies to act in concert to preserve their freedom

If collective security institutions do falter, what will this mean for the future of war and peace? Here again, the research is uncertain. While some scholars point to evidence that collective security organizations have been essential to peace, others suggest that these institutions often fail to deter violence. Still others suggest that collective security institutions might increase the possibility of wars, dragging countries into conflicts that they would not have otherwise fought. 

These debates illustrate how difficult it is to show causality in international relations. To test the effectiveness of a collective security institution, scholars have to find ways to show that a war could have occurred in its absence. In the absence of NATO, for instance, would the Soviet Union have invaded West Germany in the 1950s? Of course, it’s hard enough to explain the cause of events that happen, much less the cause of those that fail to occur.

Further reading

Last updated March 10, 2024

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