Since the beginning of Russia’s full-scale invasion of Ukraine, NATO has shown more unity and resilience than it has in years. Its purpose is clear, its strategy is unified, and what once seemed like vast chasms between its members now seem neither so deep nor so wide. Despite the criminal and gut-wrenching violence in Ukraine, NATO is strong, and must use its strength in this moment with judgment and celerity.

The Russian invasion of Ukraine will transform the European security landscape for years to come. Notwithstanding the clear, united warnings to Russian President Vladimir Putin that his actions would have severe consequences, the reality is that Putin was never going to be deterred. His megalomania and narcissistic need to right the alleged wrongs imposed on Russia after 1991 led him down this tragic path.

There is a danger, however, in concluding that the failure of deterrence somehow means that NATO has lost its value. That would concede victory to Putin by rewarding him what he most dearly desires: the destruction of NATO, the weakening of America’s security presence in Europe, and the closing the alliance’s “open door” policy, after nearly 25 years, to those nations that want to join. To assume NATO’s diminishment or demise would also yield to Putin’s demands for more influence in Europe’s security architecture, which would only make Europe even less secure.

In fact, this may be the strongest NATO has been since 1991. Regarding Ukraine, NATO’s leaders expressed solidarity and unity in standing up to Putin’s threats. Apart from their consistent and coordinated warnings against a full-scale invasion, numerous NATO heads of state engaged Putin directly to try to avert the escalation of the war.

Since the beginning of the new Russian offensive, NATO’s unity has not faltered; its cohesion has strengthened. NATO met in an extraordinary summit and activated (for the first time on European territory) the 40,000-man NATO Response Force. As part of this NRF deployment, the United States and other member states are sending forces to protect the alliance’s easternmost neighbors, including the Baltics, Poland, and Romania. Individual NATO member states are facilitating humanitarian assistance to displaced Ukrainians, and some—including, in a surprising reversal of longstanding policy, Germany—are also providing military aid to Ukraine.

None of this means that NATO has decided to move beyond its borders. Collectively, the organization decided weeks ago that it would not intervene directly in a Russia-Ukraine conflict. As a result, some critics are arguing NATO has failed Ukraine. This is based on a misunderstanding of NATO’s obligations to its non-member partners. NATO is a membership organization. The ultimate strength of NATO is its security guarantee written into Article 5 of its founding Treaty. Article 5 simply but powerfully states that an attack on one member is considered an attack on all members. This commitment contributed to the West’s victory over the Soviet Union in the Cold War and has helped to maintain peace and stability as well as encouraged democracy and economic reforms across Europe since 1991.

NATO, as a political-military alliance made up of sovereign member states responsible to their national electorates, cannot make such guarantees lightly. The alliance is not an organization that sits above national governments. Its strength derives from the legitimacy of the democratically elected civilians who control its militaries and choose new members by consensus. Members must also meet military and governance criteria to join. For its security commitments to be credible, the alliance cannot grant them to countries outside the membership organization.

Since the beginning of the Partnership for Peace program in 1994, NATO has extended a hand to former Soviet and Soviet-satellite states as well as those that maintained neutrality during the Cold War. Many have gone on to join the alliance. Others have chosen to maintain a relationship with NATO without applying for full membership. Still others, most notably Georgia and Ukraine, have been encouraged to have closer ties with NATO and, as the alliance leadership stated at the Bucharest NATO Summit in 2008, been promised eventual NATO membership (though with no timeline attached).

Ukraine is a NATO partner but not a NATO member; the Article 5 commitment does not apply. For nearly 15 years, the United States and Europe have sent conflicting messages to Kyiv about how much they want Ukraine in its institutions, such as NATO and the EU. The 2008 promise of eventual membership to Georgia and Ukraine was a compromise position between those members that wanted to admit them to the alliance and those that did not. Within months of the Bucharest announcement, Russia invaded Georgia, annexed two of its provinces constituting one-fifth of its territory, and derailed Georgia’s further integration into NATO and the EU. In 2014, Russia took similar actions in Crimea and eastern Ukraine with the same results. NATO did not intervene military in either of those wars, but condemned Russia for violating the territorial integrity of each nation. NATO continued to signal that the door remained open for future membership, and significant numbers of Georgians and Ukrainians continued to believe their future lay in NATO and the EU.

“Diplomacy is Isolation. Assistance Is Oppression. War Is Security.”

Post-Soviet Russia, too, had multiple opportunities to integrate into the transatlantic community. It joined Partnership for Peace in 1994. The alliance created the NATO-Russia Permanent Joint Council in 1997, which became the NATO-Russia Council in 2002, to give Russia a voice (but not a vote) in the alliance’s deliberations. Had Russia chosen to work cooperatively and constructively, it might have strengthened that voice. The EU also developed close relations with Russia. There was hope in the 1990s and early 2000s that Moscow might embrace the role of a responsible stakeholder in Europe—even a NATO member—but Putin chose another path.

What Putin has said and done in the past year has only reconfirmed that he is untrustworthy and dangerous, and that he has no interest in Russia being part of the transatlantic community. His grievance-laden speeches suggesting that the West has systematically abused and disadvantaged Russia should be ignored. They are based on a skewed and bad-faith reading of recent (and, for that matter, medieval) history that totally discounts the massive Western support for Russia’s transition from communism in the 1990s.

Putin wants to reduce or eliminate U.S. and allied forces on the territories of the former Warsaw Pact nations, but Russia’s actions in Belarus and Ukraine demonstrate precisely why such NATO forces are now urgently needed to reinforce NATO’s frontline states. Putin’s demand that NATO close its door to future members should be roundly ignored given his record of unprovoked and premeditated aggression against Russia’s neighbors. Membership in NATO is the only way countries bordering Russia can feel secure.

Despite Putin’s desires, there can never be a pan-European order which provides security for the rest of Europe if Moscow holds the pen or sets the terms. Ukraine’s desperate struggle today represents Moscow’s vision of security.

What Should NATO Do Now?

Now is the time for NATO to reaffirm its Article 5 commitments. Its core obligation is to defend its members. As a key aspect in maintaining peaceful relations with non-member neighbors, it also has taken on the important duty of supporting its partners bordering Russia, notably including Finland and Sweden, in part by keeping the door to membership open. As in 2008, when Russia invaded Georgia, NATO must do whatever it can to stop Russian aggression, express support and solidarity with its allies and partners on the front line, and, in the long term, roll back Russian gains.

Beyond its member states, NATO should continue to provide military equipment and humanitarian support to those fighting against Russian domination and to ensure NATO’s eastern flank remains solidly defended.

What Putin craves is for a new Russian empire to be recognized as a great power. He should be isolated on the world stage, denied a voice in transatlantic security dialogues, and surrounded by a stable circle of democracies.

In June, Spain will host a NATO Summit that will unveil the latest version of its Strategic Concept, a document that is meant to guide NATO’s ambitions for a decade or more. The last Strategic Concept was promulgated in 2010. The most important element of that document should be formally identifying Russia as the foremost threat to transatlantic security. In 2017, the NATO Secretary General said Russia was not a threat. Today, the Alliance needs to affirm that Russia is without question the biggest threat to stability and security in Europe, and to develop the mechanisms and policies to guarantee its members’ safety and security.

NATO should also reaffirm its open door to those nations that meet the its established criteria. This would of course include countries such as Sweden and Finland, now the subject of explicit threats the Russian government. Some will argue that, by proffering theoretical future membership, NATO is setting these nations up to be attacked by Moscow as Georgia and Ukraine were. But retreating from the open door policy because of Putin’s actions in Ukraine only rewards his naked aggression and dashes the hopes of millions who want to be part of the greater transatlantic community.

In the lead up to the Summit, NATO should reaffirm the suspension of the NATO-Russian Council that dates to Russia’s seizure of Crimea and destabilization of eastern Ukraine in 2014. Russia has suspended its mission to NATO and ordered NATO’s office in Moscow to be closed. There is no point in maintaining the fiction that Putin or his flunkies have any interest in an institutional link with NATO. But it is worth preserving the promise and hope that a post-Putin Russia that returns to a democratic trajectory can be a partner and even a member of NATO if it stops oppressing its neighbors.

NATO will need to address the security issues it thought it resolved in the NATO-Russia Founding Act. Chief among these will be the forward deployment of major combat units on the territory of new member states and the potential stationing of conventional short- and intermediate-range ballistic missiles. For now, the issue of forward deployment of nuclear systems may not be necessary, but NATO should preserve its right to do so if Russia continues to make both implicit and explicit nuclear threats.

NATO is more unified today in the face of Russian aggression than it has been in decades. The Summit in four months is an important opportunity to focus the alliance’s attention on its core mission of mutual defense. Putin’s actions have presented NATO’s leaders with the chance to reinvigorate the alliance and to take steps to protect a Europe whole, free, and, hopefully, at peace. If NATO’s leaders fail to seize the moment and treat the 2022 Madrid Summit like any other, they will do serious damage to the European security order, and by extension global security. If, however, NATO succeeds in reinforcing the alliance’s deterrent position and recommits to the common defense and security of Europe, it is quite possible Putin’s actions in Ukraine will bring about an even stronger alliance than he ever feared he would face.

Eric Edelman and Daniel Fata

Eric S. Edelman is Counselor at the Center for Strategic and Budgetary Assessments and a non-resident Senior Fellow at the Miller Center of Public Affairs at the University of Virginia. He is also the co-host of The Bulwark’s Shield of the Republic podcast. He was under secretary of defense for policy from 2005 to 2009. Daniel Fata is the former deputy assistant secretary of defense for Europe and NATO policy under President George W. Bush. He is currently a non-resident senior advisor at the Center for International and Security Studies in Washington, D.C. The views expressed are entirely his own.