How did NATO enlargement happen? Three case studies

In the past few years, the question of NATO enlargement has become, it can be said without exaggeration, a matter of life and death. Whether directly or indirectly, the prospect of a possible Ukraine’s NATO accession provoked the war that is currently ravaging the country. Defenders of NATO and Western values, of course, insist that the war in Ukraine has absolutely nothing to do with NATO.

But NATO Secretary General Jens Stoltenberg, presumably inadvertently, admitted just the opposite when speaking in front of a joint committee of the European Parliament in September 2023. Stoltenberg mentioned a draft treaty that Russia had sent to NATO: “The background was that President Putin declared in the autumn of 2021, and actually sent a draft treaty that they wanted NATO to sign, to promise no more NATO enlargement”, as a “pre-condition for not invade [sic] Ukraine”. Stoltenberg went on to proudly boast that “of course we didn't sign that”. The question of prospective Ukrainian accession to the alliance was not something that NATO was willing to negotiate on with Russia, regardless of what may happen to Ukraine.

But the issue of NATO enlargement remains deeply polarising. For most people in Europe, until very recently NATO was little more than a technicality, something that did not immediately affect their lives and which they could simply ignore. The war in Ukraine demonstrated that NATO is a matter that can have huge repercussions on people’s lives. NATO is simply too powerful and pervasive to be dismissed as an irrelevant superstructure with little clout on society. Different groups within the populations of European countries, however, have very divergent opinions about NATO, its function and its role in European security.

The Euro-Atlanticist camp to this day sees in the union between Europe and America a natural symbiosis, an inevitable fact of life, the natural culmination of the triumph of liberal democracy and the end of history. This group tends to be persuaded of the fact that NATO is a purely defensive alliance, originally created against the Soviet Union, four years after the end of WWII. Convinced Euro-Atlanticists argue that the very idea of “NATO expansion” after 1991 is preposterous: NATO was simply the natural aspiration of countries that had just been liberated from Soviet rule. NATO’s “open door policy” was simply a benign gesture towards groups that wanted to join an elite club of free and prosperous nations. NATO-sceptics instead argue that NATO expansion was an imperial move, the natural absorption movement of a polity that after the “victory” in the Cold War became intoxicated with its own power and recklessly expanded. It deliberately chose to ignore the security interests of Russia, simply because it could, because it felt strong and powerful, and thereby provoked the Ukraine war. Euro-Atlanticists, of course, vehemently reject such claims, arguing that the connection between NATO expansion and the Ukraine war is nothing but a “Russian lie”.

This article will analyse the historical record of NATO expansion considering three case studies, each significant for its own reasons. How did NATO expansion happen and what were the motives behind it? Did it originate from NATO? Or did the countries of the former Eastern half of Europe decide to join, unable to resist NATO’s charm? According to NATO Article 10, “once the Allies have decided to invite a country to become a member of NATO, they officially invite the country to begin accession talks with the Alliance. This is the first step in the accession process on the way to formal membership”.

An additional section will be devoted to Ukraine and Georgia, two countries that did not become NATO members — at least de jure — but which still enjoyed a privileged relationship with NATO and to whom NATO promised membership in 2008.

Hungary

Hungary joined NATO on 12 March 1999, together with Poland and the Czech Republic. It was the first NATO enlargement since the end of the Cold War. Less than 10 years after the collapse of Communism in Eastern Europe and the reunification of Germany, the promise that NATO “would expand not one inch eastward” was already ignored. Today, the sole idea of a “promise” is performatively dismissed as propaganda, arguing that even Gorbachev denied this. But the historical record says otherwise, even if it was a sort of gentleman’s agreement, not formalised in a treaty.

During the 1980s, the Hungarian Socialist Workers’ Party had already embarked on limited economic reforms under the so-called “Goulash Communism”. Hungary was one of the more liberal states in the Eastern Bloc, allowing greater economic flexibility and more freedom than existed elsewhere in Eastern Europe. By the late 1980s, however, the country’s economic situation had deteriorated. Foreign debt had reached alarming levels, growth had stagnated, and confidence in the communist system had eroded.

The first free parliamentary elections took place in 1990. The winner was the Hungarian Democratic Forum (MDF), a conservative-national movement led by József Antall. His government confronted enormous challenges. Like in many of the former Communist countries, the transition to a market economy caused factory closures, unemployment, inflation, and social insecurity. Entire sectors that had depended on the socialist economic system became uncompetitive. The Warsaw Pact was formally dissolved in July 1991. Soviet troops had already completed their withdrawal from Hungary shortly beforehand. Their departure created a vacuum.

Then in 1991 Yugoslavia began to descend into chaos. Hungary shared a border with the disintegrating federation. The conflict demonstrated that the end of the Cold War had not ushered in an era of peace. For Hungary, the wars reinforced the perception that small states in Central Europe needed external security guarantees. This concern was particularly strong because substantial Hungarian minorities lived outside Hungary’s borders, especially in Serbia, Romania and Slovakia. The Yugoslav crisis therefore strengthened arguments in favour of integration into Western institutions. As early as 1990 and 1991, leading Hungarian politicians began discussing eventual membership. However, accession was not immediately realistic. The Soviet Union still existed until December 1991, and there was uncertainty about how Russia would react.

In 1994 Hungary joined NATO's Partnership for Peace programme. This initiative allowed non-member countries to cooperate militarily with the alliance, participate in exercises, and align military standards without receiving collective defence guarantees. It was 1994 — even Russia at the time joined the Partnership for Peace initiative.

In 1994, the Hungarian Socialist Party, successor to the former communist party, won elections and formed a government under Gyula Horn. Horn himself had once been a communist official. Yet his government continued the pursuit of NATO membership with little hesitation. Washington emerged as the strongest advocate of NATO enlargement. The administration of President Bill Clinton argued that NATO expansion would stabilize Central Europe and consolidate democratic reforms. Some American diplomats and strategists warned that enlargement could damage relations with Russia. Others questioned whether NATO was extending security guarantees to countries whose defense might prove difficult in a crisis.

In 1995, NATO produced a Study on Enlargement. In this it was argued that: “With the end of the Cold War, there is a unique opportunity to build an improved security architecture in the whole of the Euro-Atlantic area. The aim of an improved security architecture is to provide increased stability and security for all in the Euro-Atlantic area, without recreating dividing lines. NATO views security as a broad concept embracing political and economic, as well as defence, components”. Russia consistently opposed expansion. Even the “philo-American” President Boris Yeltsin repeatedly argued that moving NATO eastward violated the spirit of post-Cold War cooperation.

The Madrid Summit of 1997 and the referendum on NATO

The decisive moment arrived in July 1997 at the NATO summit in Madrid. NATO formally invited Hungary, Poland and the Czech Republic. The Hungarian government organized a national referendum. Hungary was in fact one of the few countries which held a referendum on NATO. The vote took place on 16 November 1997. Official results showed approximately 85 percent support among those who participated. However, turnout was low, around 49 percent.

On 12 March 1999, under Viktor Orbán, who at the time had just been elected Prime Minister for the first time, the same Viktor Orbán that later enemies would dismiss as “Putin’s puppet”, Hungary officially became a NATO member. It was a fateful month for NATO. Only twelve days later, NATO launched its air campaign against Yugoslavia over Kosovo, NATO’s first out of area mission. After the intervention in Yugoslavia, it became difficult to argue that NATO was a purely defensive alliance. Russia took notice.

Croatia

Croatia joined NATO in 2009, together with Albania. The new state of Croatia was born through the violent disintegration of Yugoslavia. During much of the 1990s, some Western governments had viewed Croatia with suspicion. The exception was Germany. By the late 1980s, nationalism began replacing communist ideology as the principal source of political legitimacy throughout the Yugoslav federation. In Croatia, the first opposition parties emerged in 1989. The most important was the Croatian Democratic Union (HDZ), led by Franjo Tuđman. In the first multiparty elections of 1990, HDZ defeated the reformed communists and became the dominant political force.

In May 1991, Croatian voters approved independence in a referendum largely boycotted by much of the large Serbian minority in the country. Croatia formally declared independence in June 1991. War ensued. The conflict involved Croatian forces, local Serb militias and the Yugoslav People’s Army (JNA). Large parts of Croatian territory fell outside Zagreb’s control. Croatia’s survival would not have been possible without direct external support. One year after reunification, Germany was already showing a level of assertiveness that initially puzzled even its allies. Germany saw an independent Croatia as a strategic asset and was one of the first countries to recognise Croatia’s independence. It went so far as to grant military support to Croatia in the form of large weapon deliveries, mostly via secret channels.

It is hard to see the wars in Yugoslavia as a pure, noble cause for liberation. As with most conflicts, there were many dimensions. The Croatian war of independence too generated ample accusations of human-rights abuses, authoritarian tendencies and nationalist excesses that complicated Croatia's international position.

Operation Storm

The turning point in the Croatian war of independence came in 1995. During Operation Storm, Croatian forces took most territory controlled by the self-proclaimed Republic of Serbian Krajina. The operation effectively ended the war in Croatia. Franjo Tuđman died in December 1999. Weeks later a coalition led by reform-oriented parties defeated HDZ. New leaders such as Stjepan Mesić and Ivica Račan sought to improve relations with the West.

In 2000 already, Croatia joined the Partnership for Peace programme, often seen as the first step towards NATO membership, a sort of NATO’s waiting room. Just two years later in 2002, Croatia entered NATO's Membership Action Plan. While the question of a possible referendum on NATO began to be debated in Croatian society, Prime Minister Ivo Sanader (in office 2003-09) argued that a referendum on NATO was not necessary because “the Croatian constitution does not require it”. Meanwhile “independent institutions” like Transparency International, with funding from the US Embassy, conducted a months-long PR-campaign named “Better an alliance than war” to inform Croatian citizens about “the benefits of NATO”.

The crucial breakthrough came at the NATO summit in Bucharest in April 2008. There, NATO formally invited Croatia and Albania to begin accession negotiations. Following ratification by NATO member states, on April 1 2009 Croatia officially became a member of the alliance. Prime Minister Ivo Sanader proudly stated that “this achievement would not have been possible if we had put this to a referendum”.

Eighteen years after declaring independence and fourteen years after the end of the war, a country that had emerged from the violent collapse of Yugoslavia became part of the self-described strongest military alliance in history.

Montenegro

“Russia has only two allies, the army and the fleet. And Montenegro” — spurious version of a famous adage attributed to Russian Emperor Alexander III (reigned 1881-1894)

Like Serbia, with which Montenegro shares common historical and cultural ties, Montenegro historically was one of Russia’s closest allies, at least since the national liberation movement of the late nineteenth century. Montenegro’s accession to NATO in June 2017 symbolised therefore a radical turn in the small nation’s history.

In 1989, Montenegro was one of the six republics of the Socialist Federal Republic of Yugoslavia (Socialist Federal Republic of Yugoslavia). Political life was still dominated by communist structures, but the system was already weakening across the federation. Unlike Croatia or Slovenia, Montenegro did not develop a strong separatist movement in the early phase of Yugoslavia’s collapse. Its political elite largely aligned with the Serbian leadership under Slobodan Milošević, supporting the idea of a restructured Yugoslav federation dominated by Serbia and Montenegro. When Slovenia, Croatia, Bosnia and Herzegovina, and Macedonia moved toward independence, Montenegro remained within a reduced federal structure alongside Serbia. After the breakup of Yugoslavia, Montenegro became part of the Federal Republic of Yugoslavia (FRY) in 1992, together with Serbia.

During this period, the FRY was politically isolated due to the Yugoslav wars, sanctions, and conflicts in Bosnia and Croatia. Montenegro too was affected by the broader international isolation of the federation. Internally, Montenegro was governed by the Democratic Party of Socialists (DPS), led by Milo Đukanović and Momir Bulatović. By the mid-1990s, Đukanović gradually distanced himself from Serbia, especially as the costs of international isolation became more visible. At the same time, Đukanović himself had his own dodgy sides. He was repeatedly indicted in Italy for allegedly being involved in cigarette smuggling, a criminal trade that could earn one millions at the time.

In 1997, Milo Đukanović consolidated control over the DPS. Đukanović’s leadership increasingly oriented Montenegro toward Western institutions, while still formally remaining within the FRY. Montenegro adopted a pragmatic stance toward the West, especially in contrast to Serbia under Milošević, which remained under heavy sanctions and political pressure. This, however, did not protect Montenegro from NATO’s fury in the spring of 1999, when in reaction to trouble in Kosovo, NATO bombed Yugoslavia. During its 78-day bombing campaign NATO struck targets in Montenegro too.

Then in 2000 Serbian leader Milošević fell after elections and widespread protests in the country. The relationship between Serbia and Montenegro entered a new phase. First, the Federal Republic of Yugoslavia was restructured into the State Union of Serbia and Montenegro. Then, in May 2006, Montenegro held an independence referendum. A narrow majority voted in favour of independence, and Montenegro formally became a sovereign state. A new nation was born. Montenegro was now a very small state on the Adriatic coast, surrounded by NATO members or NATO-aspiring states, and with limited military capacity. The country joined NATO’s Partnership for Peace programme in 2006.

Domestic opinion on NATO was divided. People wondered why they should become part of an alliance that had bombed them only a few years before. Yet the Montenegrin ruling class put all its bets on integration with NATO. By the late 2000s and early 2010s, NATO had already incorporated most of Central and Eastern Europe, as well as several Balkan states including Croatia and Albania. Montenegro’s strategic significance was based on geography: its Adriatic coastline and its position between NATO members Croatia, Albania, and Italy.

While the government under Đukanović consistently supported NATO integration, opposition parties remained skeptical or explicitly opposed. Montenegro never developed a broad societal consensus on NATO membership. Accession was driven primarily by elite-level decision-making and external alignment rather than domestic demand. In December 2015, NATO formally invited Montenegro to begin accession negotiations. Repeated allegations of corruption and authoritarianism against Đukanović were not much of a problem. The Montenegrin Prime Minister also played “the Russian card”: on the day of the elections in 2016, allegations emerged about a Russia-inspired coup attempt against Đukanović. All the accusations were later dismissed by the Montenegrin courts. On 5 June 2017, Montenegro officially became the 29th member of NATO.

Georgia and Ukraine

Georgia and Ukraine are not NATO members today. But as early as 2008, at the Bucharest Summit, NATO had declared that both countries would eventually become members.

The government of Georgia, which had come to power four years earlier in a popular revolution, strongly supported the initiative. Georgian President Mikheil Saakashvili openly pursued NATO membership as a cornerstone of national strategy. A few months after the Bucharest Summit, Saakashvili tried to take South Ossetia, a territory that, while being recognised as part of Georgia by most countries, Georgia had not controlled since the war in 1992. However, Saakashvili’s attempt to conquer South Ossetia failed when Russia intervened on August 8 2008. Within five days Russia forced Georgia to back down. In 2013 the candidate of the opposition party “Georgian Dream”, which favoured more pragmatic relations with Russia, won the election. Georgian Dream has been the dominant force in Georgia’s political landscape ever since and talks of a future NATO membership for Georgia have been off the table.

The case of Ukraine is much more complicated. Until early 2014, before the Maidan Revolution, the idea of joining NATO would have appeared absurd to many Ukrainians, particularly, but not only, in the eastern and southern regions of the country. When in 2006, after the first Ukrainian pro-Western Revolution, NATO forces planned exercises and war games in Crimea, locals demonstrated for weeks and in the end forced US personnel to leave without completing the exercise. A vast majority of Ukrainians continued to be hostile to the idea of a possible NATO membership until the Revolution of 2014 that altered the course of Ukrainian history forever.

Within NATO too there was disagreement. Germany and France resisted granting Ukraine an immediate Membership Action Plan, fearing confrontation with Russia. Most people understood that a Ukraine in NATO would be a red line for Moscow. The American Ambassador to Russia William Burns said as much in a famous cable that went down in history as “Nyet means Nyet”. Yet, NATO’s interest in Ukraine was too strong to be concerned about these inconveniences. The world is experiencing the consequences of these fateful choices now. NATO prides itself on being an alliance of free and democratic nations, yet the experience of NATO enlargement proves that politics does indeed make strange bedfellows.