The United States was a driving force behind the formation of NATO in 1949. The alliance was initially made up of just 12 countries — including Britain, France, Italy, the Netherlands, Canada and the United States — and was designed to bolster security in Western Europe among countries worried about Soviet advances. It rested on the principle of collective defense, meaning that an attack on one member nation was an attack against all. When West Germany joined the alliance in 1955, it prompted the Soviet Union and seven of its satellite nations to establish the Warsaw Pact, a mutual defense organization. But then the Soviet Union collapsed in 1991 and the Warsaw Pact dissolved along with it. Since then, NATO has grown to include 30 countries, among them ex-Soviet republics such as Estonia, Latvia and Lithuania, as well as former satellite states Poland, Hungary and the Czech Republic. It does not have its own armed forces but instead maintains an integrated military command structure from all member states. NATO’s top general — or “supreme allied commander” — is traditionally American, while the role of secretary general is normally fulfilled by a senior European political figure. The current secretary general is a former Norwegian prime minister, Jens Stoltenberg. Before Russia’s invasion of Ukraine, NATO had spent years engaged in peacekeeping, military and training and advising missions in places such as Afghanistan, Ethiopia, Kosovo and Iraq. Then in 2014, after Russia annexed the Crimean Peninsula from Ukraine, NATO began conducting patrols over the Baltic states. Now, Russia’s full-blown invasion of the country has reinvigorated the alliance and galvanized support among member nations for a more robust troop presence on the European continent. At an extraordinary meeting of NATO defense ministers Wednesday, Stoltenberg said they discussed a new plan to expand the alliance’s forces. Member countries are considering the long-term deployment of additional troops, warships and planes to NATO’s eastern flank, he said, citing what he called the “new security reality” of a more aggressive Russia.

What is Ukraine’s position with NATO?

In 2008, NATO announced that Ukraine and Georgia would become members — once they reached the alliance’s standards for governance and transparency, among other measures. Ukraine enacted a law in 2017 making NATO membership a priority, but the nation has not progressed in its bid for membership. Some have cited Ukraine’s entrenched corruption and still-shaky transition to democracy as reasons for the delay. But NATO members have also been afraid of the Russian reaction. Nonetheless, NATO sees helping to defend Ukraine against Russian aggression as part of its mandate. When Russia annexed Crimea and invaded eastern Ukraine in 2014, NATO responded by suspending cooperation with Russia and boosting Kyiv’s defensive capabilities : NATO held military trainings, deployed troops around Eastern Europe, funded cyberwarfare preparedness and supported reforms of the Ukrainian armed forces, among other programs. Ukraine’s push for membership in NATO is one of the reasons Russia has cited to justify its invasion. And Russian President Vladimir Putin has demanded a firm promise that Ukraine will never join NATO. Since Russia’s annexation of Crimea in 2014, the issue of Ukraine’s potential NATO membership has risen in urgency. As of 2020, Ukraine has officially been one of six NATO “Enhanced Opportunities Partners,” which gives it a “tailor-made” relationship with NATO as a nonmember. Since becoming president in 2019, Zelensky has urged NATO members to accelerate Ukraine’s membership into the military alliance. In 2021, he said, “Every day we prove that we are ready to be in the alliance more than most of the countries of the European Union.” After the Russian invasion began, Zelensky said, he asked 27 European leaders whether Ukraine would join NATO. “I have asked directly. Everyone is afraid; no one answers,” Zelensky said . As the invasion has progressed, Zelensky has stressed that NATO membership is not an immediate option for Ukraine. “I have cooled down regarding this question a long time ago after we understood that … NATO is not prepared to accept Ukraine,” Zelensky said in an interview that aired March 7 on ABC News. “It is clear that Ukraine is not a member of NATO; we understand this. … For years we heard about the apparently open door, but have already also heard that we will not enter there, and these are truths and must be acknowledged,” Zelensky said during a speech before the leaders of the Joint Expeditionary Force (JEF).

Why is it difficult for Ukraine to join NATO?

NATO enlargement is a contentious issue. Since the 1990s, analysts have been concerned about its impact on NATO cohesion and solidarity, as well as relations with other nations, notably Russia, according to the NATO website. A major reason Ukraine struggled in its bid to join NATO was Kyiv’s active, unresolved border dispute with Moscow. Since 2014, Russia has backed separatists controlling the eastern regions of Luhansk and Donetsk. This border dispute put into question NATO’s role should Ukraine become a member nation. Putin also considers NATO expansion to be a “red line” for Russia, and he has accused the military alliance of trying to “encircle” Russia. Given this, Ukraine’s membership could provoke a Russian retaliation — a risk that many member states are not willing to take. The process of joining itself is complex, with a high entry bar . Still, NATO has an “open door policy,” with membership open to any “European State in a position to further the principles of this Treaty and to contribute to the security of the North Atlantic area,” per the alliance’s treaty. Any decision on enlargement must be made “by unanimous agreement.” Invitations are made “on the basis of consensus among all Allies,” and “ no third country has a say in such deliberations.” Aspiring members can join NATO’s advice and assistance program — the Membership Action Plan — in which progress on preparations is reported and assessed. Zelensky in July 2021 said Ukraine had done everything necessary to earn a NATO membership action plan. Only Bosnia is currently participating. The membership process begins with accession talks with a NATO team, to discuss aspirations, obligations and contribution to NATO’s budget. Nations then send NATO a letter of intent with a timetable for the completion of reforms. Criteria to join include rule of law standards such as “a functioning democratic political system based on a market economy” and “fair treatment of minority populations,” for example, as well as high standards on military equipment and interoperability with NATO forces. NATO prepares amendments to its founding treaty, which member state governments must ratify according to national requirements. These vary by country: In the United States, it’s a two-thirds Senate majority. In Britain, no formal parliamentary vote is needed, according to the alliance’s website . Most recently, the Republic of North Macedonia joined NATO in March 2020. The official accession process took nearly two years, with NATO leaders having agreed to begin formal accession talks in July 2018. It had been participating in the Membership Action Plan since 1999. With a green light from its leaders, Finland has taken the first step in the formal membership process — and the proposal will require approval from the nation’s parliament. NATO Secretary General Jens Stoltenberg said if Finland were to apply, the NATO ascension process would be “smooth and swift.” “Finland’s accession to NATO will cause serious damage to bilateral Russian-Finnish relations” and the “stability and security” of northern Europe, Russia’s Foreign Ministry said in a Thursday statement. “Russia will be forced to take retaliatory steps, both of a military-technical and other nature, in order to stop the threats to its national security that arise in this regard.” Missy Ryan, Tony Romm and Erin Cunningham in Washington, Annabelle Timsit in London and Emily Rauhala in Brussels contributed to this report, which has been updated.

Europe

What is NATO, and why isn’t Ukraine a member?

By Miriam Berger

Claire Parker

and

Sammy Westfall

Updated May 12, 2022 at 2:53 p.m. EDT|Published February 1, 2022 at 12:52 p.m. EST

Military trucks carry British tanks at Estonia's NATO battle group base in Tapa, Estonia, on Feb. 25. (Sergei Stepanov/AP)

In the weeks leading up to Russia’s invasion of Ukraine, the North Atlantic Treaty Organization, a military alliance of mainly Western countries, deployed thousands of additional troops to Eastern Europe to shore up its defenses.

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Since then, member countries have delivered weapons, ammunition and other military aid to Ukrainian forces.

NATO ministers discuss boosting Ukraine — and avoiding a wider war

But Ukraine does not belong to NATO, whose 30 members are united by a mutual defense treaty. And post-Cold War tensions between the West and Russia over the alliance’s eastward expansion — including to countries that were once part of the Soviet Union — are at the heart of the current crisis.

Ukraine has made clear its desire to join NATO, even rewriting the constitution to enshrine its commitment. Russia, however, sees NATO enlargement as an existential threat and has demanded that Ukraine be barred from ever becoming a member.

Russian President Vladimir Putin has called the expansion of NATO a “red line” for him, and has cited it as a reason for invading Ukraine.

Though Ukraine has backed away from seeking immediate membership into the alliance, two other countries — Finland and Sweden, both traditionally nonaligned — have been inching closer to joining NATO.

On Thursday, Finland’s leaders announced that they would seek NATO membership as soon as possible — an extraordinary move that would double the alliance’s land border with Russia. The Kremlin immediately hit back, saying Finland’s accession to NATO would “definitely” threaten Russia’s security.

“The expansion of NATO does not make our continent more stable and secure,” Kremlin spokesman Dmitry Peskov told journalists Thursday, according to Russian news outlet Interfax. He added that Russia could take new measures to “balance the situation” if Finland joins the alliance.

Here is some essential background about NATO and how nations are able to join.

How joining NATO and the E.U. became Ukraine’s unattainable dream

What is NATO, and why isn’t Ukraine a member?

War in Ukraine: What you need to know