My policy was to work for the best, while expanding NATO to prepare for the worst.

When I first became president, I said that I would support Russian President Boris Yeltsin in his efforts to build a good economy and a functioning democracy after the dissolution of the Soviet Union—but I would also support an expansion of NATO to include former Warsaw Pact members and post-Soviet states. My policy was to work for the best while preparing for the worst. I was worried not about a Russian return to communism, but about a return to ultranationalism, replacing democracy and cooperation with aspirations to empire, like Peter the Great and Catherine the Great. I didn’t believe Yeltsin would do that, but who knew what would come after him?

If Russia stayed on a path toward democracy and cooperation, we would all be together in meeting the security challenges of our time: terrorism; ethnic, religious, and other tribal conflicts; and the proliferation of nuclear, chemical, and biological weapons. If Russia chose to revert to ultranationalist imperialism, an enlarged NATO and a growing European Union would bolster the continent’s security. Near the end of my second term, in 1999, Poland, Hungary, and the Czech Republic joined NATO despite Russian opposition. The alliance gained 11 more members under subsequent administrations, again over Russian objections.

Lately, NATO expansion has been criticized in some quarters for provoking Russia and even laying the groundwork for Vladimir Putin’s invasion of Ukraine. The expansion certainly was a consequential decision, one that I continue to believe was correct.

As United Nations ambassador and later secretary of state, my friend Madeleine Albright, who recently passed away, was an outspoken supporter of NATO expansion. So were Secretary of State Warren Christopher; National Security Adviser Tony Lake; his successor, Sandy Berger; and two others with firsthand experience in the area: Chairman of the Joint Chiefs of Staff John Shalikashvili, who was born in Poland to Georgian parents and came to the U.S. as a teenager, and Deputy Secretary of State Strobe Talbott, who translated and edited Nikita Khrushchev’s memoirs while we were housemates at Oxford in 1969 and 1970.

At the time I proposed NATO expansion, however, there was a lot of respected opinion on the other side. The legendary diplomat George Kennan, famous for advocating for the policy of containment during the Cold War, argued that with the fall of the Berlin Wall and the dissolution of the Warsaw Pact, NATO had outlived its usefulness. The New York Times columnist Tom Friedman said Russia would feel humiliated and cornered by an enlarged NATO, and when it recovered from the economic weakness of the last years of Communist rule, we would see a terrible reaction. Mike Mandelbaum, a respected authority on Russia, thought it was a mistake too, arguing that it wouldn’t promote democracy or capitalism.

I understood that renewed conflict was a possibility. But in my view, whether it happened depended less on NATO and more on whether Russia remained a democracy and how it defined its greatness in the 21st century. Would it build a modern economy based on its human talent in science, technology, and the arts, or seek to re-create a version of its 18th-century empire fueled by natural resources and characterized by a strong authoritarian government with a powerful military?

I did everything I could to help Russia make the right choice and become a great 21st-century democracy. My first trip outside the United States as president was to Vancouver to meet with Yeltsin and guarantee $1.6 billion for Russia so it could afford to bring its soldiers home from the Baltic states and provide for their housing. In 1994, Russia became the first country to join the Partnership for Peace, a program for practical bilateral cooperation, including joint training exercises between NATO and non-NATO European countries. That same year, the U.S. signed the Budapest Memorandum, along with Russia and the United Kingdom, which guaranteed Ukraine’s sovereignty and territorial integrity in return for Ukraine’s agreement to give up what was then the third-largest nuclear arsenal in the world. Beginning in 1995, after the Dayton Accords ended the Bosnian War, we made an agreement to add Russian troops to the peacekeeping forces that NATO had on the ground in Bosnia. In 1997, we supported the NATO-Russia Founding Act, which gave Russia a voice but not a veto in NATO affairs, and supported Russia’s entry to the G7, making it the G8. In 1999, at the end of the Kosovo conflict, Secretary of Defense Bill Cohen reached an agreement with the Russian defense minister under which Russian troops could join UN-sanctioned NATO peacekeeping forces. Throughout it all, we left the door open for Russia’s eventual membership in NATO, something I made clear to Yeltsin and later confirmed to his successor, Vladimir Putin.

In addition to all these efforts to involve Russia in NATO’s post–Cold War missions, Albright and our entire national-security team worked hard to promote positive bilateral relations. Vice President Al Gore co-chaired a commission with Russian Prime Minister Viktor Chernomyrdin to address issues of mutual interest. We agreed to destroy 34 tons of weapons-grade plutonium each. We also agreed to pull Russian, European, and NATO conventional forces back from borders, though Putin declined to go ahead with the plan when he assumed the Russian presidency in 2000.

All told, I met with Yeltsin 18 times and Putin five times—twice when he was Yeltsin’s prime minister and three times in the 10-plus months that our terms as president overlapped. That’s just three short of all the U.S.-U.S.S.R. leaders’ meetings from 1943 through 1991. The idea that we ignored, disrespected, or tried to isolate Russia is false. Yes, NATO expanded despite Russia’s objections, but expansion was about more than the U.S. relationship with Russia.

When my administration started, in 1993, no one felt certain that a post–Cold War Europe would remain peaceful, stable, and democratic. Big questions remained about East Germany’s integration with West Germany, whether old conflicts would explode across the continent as they did in the Balkans, and how former Warsaw Pact nations and newly independent Soviet republics would seek security, not just against the threat of Russian invasion, but from one another and from conflicts within their borders. The possibility of EU and NATO membership provided the greatest incentives for Central and Eastern European states to invest in political and economic reforms and abandon a go-it-alone strategy of militarization.

Neither the EU nor NATO could stay within the borders Stalin had imposed in 1945. Many countries that had been behind the Iron Curtain were seeking greater freedom, prosperity, and security with the EU and NATO, under inspiring leaders such as Václav Havel in the Czech Republic, Lech Wałęsa in Poland, and, yes, a young pro-democracy Viktor Orbán in Hungary. Thousands of everyday citizens crowded the squares of Prague, Warsaw, Budapest, Bucharest, Sofia, and beyond whenever I spoke there.

As Carl Bildt, the former Swedish prime minister and foreign minister, tweeted in December 2021, “It wasn’t NATO seeking to go East, it was former Soviet satellites and republics wishing to go West.”

Or as Havel said in 2008: “Europe is no longer, and must never again be, divided over the heads of its people and against their will into any spheres of interest or influence.” To reject Central and Eastern European countries’ membership into NATO simply because of Russian objections would have been doing just that.

Enlarging NATO required unanimous consent of the alliance’s then-16 members; two-thirds consent of a sometimes skeptical U.S. Senate; close consultation with prospective members to ensure that their military, economic, and political reforms met NATO’s high standards; and near-constant reassurance to Russia.

Madeleine Albright excelled at every step. Indeed, few diplomats have ever been so perfectly suited for the times they served as Madeleine. As a child in war-torn Europe, Madeleine and her family were twice forced to flee their home—first by Hitler, then by Stalin. She understood that the end of the Cold War provided the chance to build a Europe free, united, prosperous, and secure for the first time since nation-states arose on the continent. As UN ambassador and secretary of state, she worked to realize that vision and to beat back the religious, ethnic, and other tribal divisions that threatened it. She used every item in her famed diplomat’s toolkit and her domestic political savvy to help clear the way for the Czech Republic, Hungary, and Poland to join NATO in 1999.

The result has been more than two decades of peace and prosperity for an ever-larger portion of Europe and a strengthening of our collective security. Per capita GDPs have more than tripled in the Czech Republic, Hungary, and Poland. All three countries have participated in a variety of NATO missions since joining, including the peacekeeping force in Kosovo. To date, no member state of our defensive alliance has been invaded. Indeed, even in the early years after the fall of the Iron Curtain, the mere prospect of NATO membership helped cool long-simmering disputes between Poland and Lithuania, Hungary and Romania, and others.

Now Russia’s unprovoked and unjustified invasion of Ukraine, far from casting the wisdom of NATO expansion into doubt, proves that this policy was necessary. Russia under Putin clearly would not have been a content status quo power in the absence of expansion. It wasn’t an immediate likelihood of Ukraine joining NATO that led Putin to invade Ukraine twice—in 2014 and in February—but rather the country’s shift toward democracy that threatened his autocratic power at home, and a desire to control the valuable assets beneath the Ukrainian soil. And it is the strength of the NATO alliance, and its credible threat of defensive force, that has prevented Putin from menacing members from the Baltics to Eastern Europe. As The Atlantic’s Anne Applebaum said recently, “The expansion of NATO was the most successful, if not the only truly successful, piece of American foreign policy of the last 30 years … We would be having this fight in East Germany right now if we hadn’t done it.”

The failure of Russian democracy, and its turn to revanchism, was not catalyzed in Brussels at NATO headquarters. It was decided in Moscow by Putin. He could have used Russia’s prodigious skills in information technology to create a competitor for Silicon Valley and build a strong, diversified economy. Instead he decided to monopolize and weaponize those abilities to promote authoritarianism at home and wreak havoc abroad, including by interfering in the politics of Europe and the U.S. Only a strong NATO stands between Putin and even further aggression. We should therefore support President Joe Biden and our NATO allies in giving as much assistance to Ukraine, both military and humanitarian, as possible.

My last conversation with Madeleine Albright was just two weeks before she died. She was vintage Madeleine, sharp and direct. It was clear she wanted to go out with her boots on, supporting the Ukrainians in their fight for freedom and independence. On her declining health, she said, “I’ve got good care. I’m doing what I can. Let’s not waste time on that. The important thing is what kind of world we’re going to leave our grandchildren.” Madeleine saw her lifelong fight for democracy and security as both an obligation and an opportunity. She was proud of her Czech heritage and certain that her people and their neighbors in Central and Eastern Europe would defend their freedom, “because they know the price of losing freedom.” She was right about NATO when I was president and right about Ukraine now. I miss her so much, but I can still hear her voice. So should we all.