Tragically, it became apparent in early 2022 that a major land war in Europe was no longer a thing of the past. Russian president Vladimir Putin’s decision to launch new hostilities against Ukraine on 24 February signalled a renewed era of confrontation between an authoritarian regime in Moscow and democratic nations to its west.

February 2022 was not the first time that Putin had used force against Ukrainians, of course, but the scale of the incursion in that month was an order of magnitude larger and more brutal than previous iterations. His gruesome actions made undeniably clear that he and the state that he controls are the biggest threats to democracy and liberty in Europe.

Among other consequences, these actions caused NATO to reassess its own strategy dramatically. Prior to the February 2022 invasion, the alliance had been focused on potential future threats from China. In July, however, NATO issued a new Strategic Concept emphasising the current threat from Russia instead, describing Moscow as ‘the most significant and direct threat to Allies’ security and to peace and stability in the Euro-Atlantic area’. NATO thereby once again found itself in the role of chief defender of that peace, stability and liberty.

NATO’s return to confrontation with Russia means it has come full circle from the end of the Cold War, ending a period of cooperation and resuming confrontation and tension. How did the alliance once again find itself in this role? The answer to this question goes much further back than just February 2022. By re-examining a few key moments in the history of the Western fight with Russia over NATO’s role in Europe, we can understand the origins of today’s conflict – and how NATO might best deal with it.

Why, after a period of so much closeness and cooperation around the time of the Soviet collapse 30 years ago, did relations between Moscow and Washington deteriorate so badly? As much as we might wish for a simple answer, there is no denying that major events happen for multiple reasons.

History is rarely, if ever, monocausal. American and Russian choices interacted cumulatively with each other, and with each country’s domestic politics, to produce the decay. But it is hard to avoid the reality that one particular US policy call added to the burdens on Russia’s fragile young democracy when it was most in need of friends: the post-Cold War decision to expand NATO.

Saying this is not the same thing as saying that expansion was a mistake. The choice to enlarge the Atlantic alliance was a justifiable response to the geopolitics of the 1990s. The problem was how it happened. To understand what went wrong, it is necessary to move beyond the familiar binary – either praising or condemning enlargement wholesale – and get into the weeds of the policy’s implementation. Doing so shows how expansion carried both clear benefits and costs, and that the manner of enlargement increased the latter unnecessarily.

Put differently, the failure in US-Russian relations was not overdetermined, with both sides careening unavoidably toward renewed confrontation. Handling implementation differently could have meant both sides instead arriving, if not at a perpetually harmonious modus vivendi, then at a less toxic situation than today’s. But in the 1990s, two American presidents were so focused on achieving the eastward extension of Article 5 that they did not sufficiently consider the consequences of how they achieved that goal. As President George H W Bush said in response to the idea that Washington might compromise with Moscow over NATO’s future, ‘to hell with that’. President Bill Clinton was certain that Russia could be ‘bought off’. Along the way, a promising alternative mode of contingent enlargement that would have avoided drawing a new line across Europe fell to hardline opposition.

Given the space constraints on this essay, it is not possible to delve into the full history in detail; rather, it is necessary to focus on a few key junctures, and the year 1999 was one of them. In that year, Clinton decided to have NATO’s April 1999 summit in Washington publicly welcome the interest expressed by a host of Eastern European states, including the Baltics, in full NATO membership. This decision ultimately culminated in the so-called NATO Big Bang expansion in 2004.

Clinton made this 1999 decision at a time when the alliance was taking military action against Serbian forces in Kosovo, despite fierce Russian resistance to attacks on fellow Slavs. Clinton’s promotion of Baltic membership in particular at this tricky moment in relations with Russia meant that the alliance would extend within what Moscow considered to be the former Soviet Union itself at a time of tensions. The United States could insist, correctly, that it had never recognised the Baltics’ incorporation into the USSR, but that did not change the political import of the decision.

Nordic and Scandinavian countries privately tried to counsel caution. Because of their location in a neighbourhood that had long been Soviet adjacent but not Soviet controlled, in earlier decades Norwegians and Danes had negotiated limits on their own NATO memberships. They had, in essence, developed a Scandinavian strategy for keeping longterm frictions with Moscow manageable. They would voluntarily refrain from hosting foreign troops and nuclear weapons on their territory in peacetime to reduce tensions. Something similar would be advisable for the Baltics, they felt, as those new states were now residing in a neighbourhood that was also Russia-adjacent but not Russian controlled. Finns and Swedes emphasised this theme, warning of the need to keep frictions with Moscow manageable. But Washington was no longer interested in partial implementation of membership and proceeded with membership without any qualifications.

This fateful 1999 decision came not only at a time of tension over Kosovo. It also came at the same time that Russian president Boris Yeltsin, suffering both from heart disease and the health consequences of a drinking problem, decided to make his prime minister, Putin, acting president on the last day of 1999. Yeltsin informed Putin of this decision on 14 December, but said that Putin had to keep the news to himself until 31 December.

A week after this conversation with Yeltsin, Putin took part in an unveiling ceremony for the restored plaque of former long-time KGB head (and later Soviet leader) Yuri Andropov. The symbolism was obvious. Andropov’s formative experience had been the 1956 uprising in Hungary. He had watched in horror from the window of the Soviet embassy in Budapest as an uprising threatened to topple the Communist government and remove Hungary from the Warsaw Pact. Andropov never forgot watching the bodies of executed Hungarian secret police swaying from the streetlights. The experience marked the birth of Andropov’s so called Hungarian complex, meaning a conviction that tolerance of even small protest movements could lead to serious challenges to Moscow’s authority – a lesson Putin’s attendance highlighted once again.

The significance of Putin’s attendance at the plaque ceremony became apparent to all on New Year’s Eve 1999. That morning, Yeltsin recorded a brief resignation video, to be broadcast nationwide at noon. Even though Washington knew Putin was Yeltsin’s preferred successor, once it hit the airwaves, the hurried handover came as a shock. The US ambassador in Moscow awakened Strobe Talbott, the deputy secretary of state, at his home in Washington and told him to turn on a television. The two Americans stayed on the phone as they watched the Yeltsin era come to an end.

Yeltsin shocked the country with the news in his video. Promising that a new generation of leaders would do everything ‘bigger and better’, he disclosed that he had already signed a decree making Putin acting president. He bid farewell to his compatriots, expressing a last wish that they ‘be happy’. After watching the broadcast of his own video in the Kremlin together with Putin, Yeltsin told his successor to ‘take care of Russia’. The legacy of these events for today is manifold and profound. For starters, tensions between Moscow and Washington in 1999 helped to close the window of opportunity for comprehensive US-Russian strategic nuclear disarmament – the most significant opening since the dawn of the atomic age. By the end of the 1990s, intelligence agencies reported on the beginnings of renewed nuclear competition.

Other forms of competition emerged soon thereafter, not least in the shredding of hard-won arms control accords. And today’s permissive environment of a world almost wholly lacking such accords means both sides are reassessing the roles of not just nuclear but also conventional capabilities. In Europe in recent years, both the post-Cold War American drawdown of forces and the Russian shift of troops eastward have reversed.

Increasing tensions have also raised questions about security in cyber and economic domains. As the historian Adam Tooze has shown, renewed Russian aggression reveals that the post-Cold War ‘disavowal of the obvious connection between trade and security policy’ was a grievous error, one fully exposed by ‘the resurgence of Putin’s Russia’. Despite having a GDP not that much larger than Spain’s, once the cooperative spirit died, Russia began leveraging ‘its military assets to upend the geopolitical balance in Western Asia and the Middle East’, and its cyber capabilities to wound governments and businesses around the globe.

Viewed in conceptual terms, it is clear that the world created by the 1990s did not fulfil the hopes of 1989 – meaning, among other things, the belief that the liberal international order had succeeded definitively, and that residents of all states between the Atlantic and the Pacific, not just the Western ones, could now cooperate within it. This outcome was not fore-ordained. Instead, both American and Russian leaders repeatedly made choices yielding outcomes that not only fell short of those hopes, but were explicitly at odds with their stated intentions. In the course of the 1990s, Bush talked about a Europe whole, free, and at peace; Clinton repeatedly proclaimed his wish to avoid drawing a line. Yet with their actions, both in the end promoted a dividing line across Europe.

Gorbachev wanted to save the Soviet Union; Yeltsin wanted to democratise Russia; and both, in different ways, wanted to partner on equal footing with the West. Yet, in the longer term, both failed as well.

Residents of the former Warsaw Pact and Soviet states also experienced outcomes at odds with initial hopes. Although such states repeatedly said they did not want to end up in a grey zone, some did. The peoples of Belarus, Georgia and Ukraine all struggled to define their relations with Russia and, at times, defend their borders. Former Warsaw Pact states experienced their own uncertainties. While they succeeded in joining NATO (and eventually the European Union as well), they found that such memberships did not automatically lock in their democratic transformations and, like the rest of the continent, they suffered rising tensions with Moscow.

In the twenty-first century, what increasingly became apparent was that the pressures of simultaneously democratising and creating a market economy had produced fertile ground for latter-day, Soviet-trained authoritarians such as Putin. Once securely in power, Putin began gradually throttling back the democratic transformation while resuming old habits of competition with the West. And complaints about how NATO had moved military infrastructure to within former Soviet borders provided him with a useful rationale.

More public candour at the time from knowledgeable insiders about the options being foreclosed might have helped. Even as strong a supporter of NATO as then-senator Joseph Biden sensed that he lacked answers to key questions: enlargement, yes, but at what cost to relations with former Soviet republics, and to nuclear disarmament? Biden asked an expert witness – former US ambassador to the Soviet Union, Jack Matlock – questions to this effect at a Senate hearing on NATO expansion on 30 October, 1997. Matlock responded that, despite the passing of the Cold War, ‘the most serious potential security threat to the American people’ remained ‘weapons of mass destruction from Russian arsenals’.

Biden replied: ‘I agree with that concern.’ One-size-fits-all expansion, Matlock continued, would not help to contain that threat and could even ‘undermine the effort’. In reply, Biden concluded that ‘continuing the Partnership for Peace [an alternative to giving out full Article 5 guarantees immediately], which turned out to be much more robust and much more successful than I think anyone thought it would be at the outset, may arguably have been a better way to go’.

The Partnership might also have helped its greatest critics, the Central and Eastern European countries, towards a more permanent democratisation. Social science researchers later established that it was not NATO membership that prompted these countries to complete civil and military reforms, it was the process of trying to join. Congressional investigators and others warned that countries were entering NATO before establishing strong democratic institutions. If the Partnership had survived as originally implemented, potential allies would – admittedly through clenched teeth – have had to earn alliance status over a longer period, presumably making them more resistant to subsequent attacks on democracy.

By the end of the pivotal decade of the 1990s, the Clinton administration had instead secured an open road for extending the alliance eastward. After Clinton and his advisors left office, they could only watch in alarm as Bush’s son, George W Bush, took the keys to the NATO car and gunned it down that open road. Among other stops, the younger Bush attended the alliance’s summits in 2006 in Latvia, the first such event on former Soviet territory, and in 2008 in Bucharest, where he pushed hard for the inclusion of Georgia and Ukraine. For Putin, that Bucharest summit – coming on top of Bush’s 2003 invasion of Iraq and his 2007 decision to erect ballistic missile defences (in the form of ten ground-based interceptors in Poland and a radar facility in the Czech Republic), all around the time of ‘colour revolutions’ in post-Soviet states – proved to be the breaking point.

Since the alliance frowns on allies joining NATO to pursue pre-existing military disputes, Putin decided to escalate just such pre-existing conflicts with Georgia in 2008 and Ukraine in 2014 in violent fashion. The hope that such armed conflicts were gone for good had characterised much of the post-Cold War era. Russia’s action signalled that the era was over. Putin also expanded Russia’s conventional military budget, developed new missile defence and space capabilities, and began modernising Russia’s nuclear arsenal. In response, the alliance’s leaders suspended not only the NATO-Russia Council but ‘all practical cooperation between NATO and Russia’.

Contrasting today’s situation with other feasible outcomes to the process of reshaping order after the Cold War helps us to understand just how far short of better alternatives the current situation falls. As Russia expert Stephen Sestanovich presciently wrote in a 1993 op-ed in the New York Times, while real doubts could be raised about ‘all the many’ alternatives being proposed for cooperation with Russia, ‘these doubts are nothing compared with the frustration and powerlessness we will feel once Russian democracy fails’. We are now living with that frustration – and the risks to liberty that it entails.

What has happened cannot be undone, but it is worth learning the lessons of the past as NATO once again expands. At the time of writing, Finland and Sweden are in the process of becoming members. They are fully justified in their desire to join the alliance, just as NATO is fully justified in accepting them, complaints from Moscow notwithstanding. But they should also proceed cautiously and learn from the history above.

Sadly, a situation of tension with Russia is once again the order of the day. Finns and Swedes should follow the example of Norwegians and Danes, and find ways to become NATO members while keeping tensions with Moscow manageable. The coming conflict with Russia – a second Cold War – appears set to last for some time. Finding ways to defend Western values and liberties, this time with the Finns and Swedes as allies, but without escalation, is the major challenge now facing policymakers. It will not be easy, but success is essential.