The North Atlantic Treaty Organization (NATO)

Karl Anderson/U.S. Navy

Russian aggression in Ukraine has breathed new life into the Cold War-era security alliance, prompting allies to reinforce defenses in Eastern Europe and expand cooperation with nonmembers.

Last updated May 15, 2017

Karl Anderson/U.S. Navy
Current political and economic issues succinctly explained.


The North Atlantic Treaty Organization, a cornerstone of transatlantic security during the Cold War, has significantly recast its role in the past twenty years. Founded in 1949 as a bulwark against Soviet aggression, NATO has evolved to confront threats ranging from piracy off the Horn of Africa to maritime security in the Mediterranean. But Russian actions in recent years, particularly its 2014 intervention in Ukraine, have refocused the alliance's attention on the continent. Recent developments have also exposed unresolved tensions over NATO's expansion into the former Soviet sphere.

A Post–Cold War Pivot

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After the demise of the Soviet Union in 1991, Western leaders intensely debated the future direction of the transatlantic alliance. President Bill Clinton's administration favored expanding NATO to both extend its security umbrella to the east and consolidate democratic gains in the former Soviet bloc. On the other hand, some U.S. officials wished to peel back the Pentagon's commitments in Europe with the fading of the Soviet threat.

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NATO (North Atlantic Treaty Organization)

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Military Operations

European members were also split on the issue. London feared NATO’s expansion would dilute the alliance, while Paris believed it would give NATO too much influence. Many in France hoped to integrate former Soviet states via European institutions. There was also concern about alienating Russia.

For the White House, the decision held larger meaning. “[President Clinton] considered NATO enlargement a litmus test of whether the U.S. would remain internationally engaged and defeat the isolationist and unilateralist sentiments that were emerging,” wrote Ronald D. Asmus, one of the intellectual architects of NATO expansion, in Opening NATO's Door.

In his first trip to Europe as president, in January 1994, Clinton announced that NATO enlargement was “no longer a question of whether but when and how.” Just days before, alliance leaders approved the launch of the Partnership for Peace, a program designed to strengthen ties with Central and Eastern European countries, including many former Soviet republics like Georgia, Russia, and Ukraine.

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Beyond Collective Defense

Many defense planners also felt that a post–Cold War vision for NATO needed to look beyond collective defense—Article V of the North Atlantic Treaty states that “an armed attack against one or more [member states] in Europe or North America shall be considered an attack against them all”—and focus on confronting acute instability outside its membership. “The common denominator of all the new security problems in Europe is that they all lie beyond NATO's current borders,” said Senator Richard Lugar (R–IN) in a 1993 speech.

The common denominator of all the new security problems in Europe is that they all lie beyond NATO's current borders.
Richard Lugar, U.S. Senator from Indiana

The breakup of Yugoslavia in the early 1990s and the onset of ethnic conflict tested the alliance on this point almost immediately. What began as a mission to impose a UN-sanctioned no-fly zone over Bosnia and Herzegovina evolved into a bombing campaign on Bosnian Serb forces that many military analysts say was essential to ending the conflict. It was during Operation Deny Flight [PDF] in April 1994 that NATO conducted its first combat operations in its forty-year history, shooting down four Bosnian Serb aircraft.

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NATO Operations

In 2017, NATO pursues several missions: security assistance in Afghanistan; peacekeeping in Kosovo; maritime security patrols in the Mediterranean; support for African Union forces in Somalia; and policing the skies over eastern Europe.

Headquartered in Brussels, NATO is a consensus-based alliance, where decisions must reflect the membership's collective will. However, individual states or subgroups of allies may initiate action outside NATO auspices. For instance, France, the UK, and the United States began policing a UN-sanctioned no-fly zone in Libya in early 2011 and within days transferred command of the operation to NATO (once Turkish concerns had been allayed). Member states are not required to participate in every NATO operation. For instance, Germany and Poland declined to contribute directly to the campaign in Libya.

NATO's military structure is divided between two strategic commands: the Supreme Headquarters Allied Powers Europe, located near Mons, Belgium; and the Allied Command Transformation, located in Norfolk, Virginia. The Supreme Allied Commander Europe oversees all NATO military operations and is always a U.S. flag or general officer (currently Army General Curtis M. Scaparrotti). Although the alliance has an integrated command, most forces remain under their respective national authorities until NATO operations commence.

NATO's secretary-general (currently Norway's Jens Stoltenberg) serves a four-year term as chief administrator and international envoy. The North Atlantic Council is the alliance's principal political body, composed of high-level delegates from each member state.

Sharing the Burden

The primary financial contribution made by member states is the cost of deploying their respective armed forces for NATO-led operations. These expenses are not part of the formal NATO budget, which funds alliance infrastructure including civilian and military headquarters. In 2015, NATO members collectively spent more than $890 billion on defense [PDF]. The United States accounted for more than 70 percent of this, up from about half during the Cold War.

NATO members have committed to spending 2 percent of their annual GDP on defense, but by 2016 just five out of the twenty-eight members met this threshold—the United States (3.6), Greece (2.4), the United Kingdom (2.2), Estonia (2.2), and Poland (2). U.S. officials have regularly criticized European members for cutting their defense budgets, but the Trump administration has taken a more assertive approach, suggesting the United States may reexamine its treaty obligations if the status quo persists. “If your nations do not want to see America moderate its commitment to this alliance, each of your capitals needs to show support for our common defense,” U.S. Defense Secretary Jim Mattis told counterparts in Brussels in February 2016. 

Afghanistan and ISAF

NATO invoked its collective defense provision (Article V) for the first time following the September 11 attacks on the United States, perpetrated by the al-Qaeda terrorist network based in Afghanistan. Shortly after U.S.-led forces toppled the Taliban regime in Kabul, the UN Security Council authorized an International Security Assistance Force (ISAF) to support the new Afghan government. NATO formally assumed command of ISAF in 2003, marking its first operational commitment beyond Europe. The fact the alliance was used in Afghanistan "was revolutionary," said NATO expert Stanley Sloan in a CFR interview. “It was proof the allies have adapted [NATO] to dramatically different tasks than what was anticipated during the Cold War.”

But some critics questioned NATO's battlefield cohesion. While allies agreed on the central goals of the mission—the stabilization and reconstruction of Afghanistan—some members restricted their forces from participating in counterinsurgency and other missions, a practice known as “national caveats.” Troops from Canada, the Netherlands, the UK, and the United States saw some of the heaviest fighting and bore the most casualties, stirring resentments among alliance states. NATO commanded more than 130,000 troops from more than fifty alliance and partner countries at the height of its commitment in Afghanistan. After thirteen years of war, ISAF completed its mission in December 2014.

In early 2015, NATO and more than a dozen partner countries began a noncombat support mission of about thirteen thousand troops (roughly half are U.S.) to provide training, funding, and other assistance to the Afghan government.

Relations With Russia

Moscow has viewed NATO's post–Cold War expansion into Central and Eastern Europe with great concern. Many current and former Russian leaders believe the alliance's inroads into the former Soviet sphere are a betrayal of alleged guarantees to not expand eastward after Germany’s reunification in 1990—although some U.S. officials involved in these discussions dispute this pledge.

NATO’s Expanding Membership Map

Most Western leaders knew the risks of enlargement. “If there is a long-term danger in keeping NATO as it is, there is immediate danger in changing it too rapidly. Swift expansion of NATO eastward could make a neo-imperialist Russia a self-fulfilling prophecy,” wrote Secretary of State Warren Christopher in the Washington Post in January 1994.

Over the years, NATO and Russia took significant steps toward reconciliation, particularly with their signing of the 1997 Founding Act, which established an official forum for bilateral discussions. But a persistent lack of trust has plagued relations.

Swift expansion of NATO eastward could make a neo-imperialist Russia a self-fulfilling prophecy.
Warren Christopher, U.S. secretary of state

NATO's Bucharest Summit in the spring of 2008 deepened suspicions. While the alliance delayed Membership Action Plans for Ukraine and Georgia, it vowed to support their full membership down the road, despite repeated warnings from Moscow of political and military consequences. Russia's invasion of Georgia that summer was a clear signal of Moscow's intentions to protect what it sees as its sphere of influence, experts say.

Russia's annexation of Crimea and destabilization of eastern Ukraine in 2014–2017 have poisoned relations with NATO for the foreseeable future. “We clearly face the gravest threat to European security since the end of the Cold War,” said NATO Secretary-General Anders Fogh Rasmussen after Russia's intervention in March 2014. Weeks later, NATO suspended all civilian and military cooperation with Moscow.

In an address honoring the annexation of Crimea, President Vladimir Putin expounded Russia's deep-seated grievances with the alliance. “They have lied to us many times, made decisions behind our backs, placed us before an accomplished fact. This happened with NATO's expansion to the East, as well as the deployment of military infrastructure at our borders,” he told Russia's parliament. “In short, we have every reason to assume that the infamous [Western] policy of containment, led in the eighteenth, nineteenth, and twentieth centuries, continues today.”

In congressional testimony [PDF] in March 2017, General Scaparrotti said “a resurgent Russia has turned from partner to antagonist,” and has remained one of the top security challenges in Europe. Moscow continued to flex its military muscles in the region, he said, sending its sole aircraft carrier on its first-ever combat deployment, moving nuclear-capable missiles into Kaliningrad, and conducting significant operations in Ukraine and Syria. Meanwhile, Moscow pursued malign activities short of war, including misinformation and hacking campaigns against European member states, he said. The Kremlin has denied allegations it attempted to interfere in U.S. and European elections.

Ahead of a NATO summit in May 2017, Montenegro was expected to become the twenty-ninth member of the alliance, the first since Albania and Croatia joined in 2009. In a statement on the former Yugoslav republic’s accession, the White House noted to other NATO hopefuls “that the door to membership in the Euro-Atlantic community of nations remains open and that countries in the Western Balkans are free to choose their own future and select their own partners without outside interference or intimidation.” The Kremlin has warned that NATO’s eastward expansion “cannot but result in retaliatory actions.”

Another perennial point of contention has been NATO's ballistic missile defense shield, which is being deployed across Europe in several phases. The United States, which developed the technology, has said the system is only designed to guard against limited missile attacks, particularly from Iran. However, the Kremlin says the technology could be updated and may eventually tip the strategic balance toward the West.

A Revived Alliance

Fears of further Russian aggression have prompted alliance leaders to reinforce defenses on its eastern flank. Since its Wales Summit in 2014, NATO has ramped up military exercises and opened new command centers in eight member states: Bulgaria, Estonia, Hungary, Latvia, Lithuania, Poland, Romania, and Slovakia. The outposts, which are modestly staffed, are intended to support a new rapid reaction force of about twenty thousand, including five thousand ground troops. In a major emergency, NATO military planners say that a multinational force of about forty thousand can be marshaled. At the Warsaw Summit in 2016, allies agreed to rotate four battalions (about four thousand troops) through Poland and the Baltic states. The United States has added an Army armored brigade to the two it has in the region, under its European Reassurance Initiative.

Meanwhile, NATO members, particularly Denmark, Germany, the UK, and the United States have increased air patrols over Poland and the Baltics. In 2015, NATO jets scrambled to intercept Russian warplanes violating allied airspace some four hundred times. In 2016 this number doubled, alliance officials said.

NATO members have also boosted direct security collaboration with Ukraine, an alliance partner since 1994. But as a nonmember, Ukraine remains outside of NATO's defense perimeter, and there are clear limits on how far it can be brought into institutional structures. The UK and the United States sent modest detachments of troops to train Ukrainian personnel in 2015, but the United States has refrained from providing Kiev with lethal weapons to help counter the Russia-backed insurgency out of fear this would escalate the conflict.

In the longer term, some defense analysts believe the alliance should consider advancing membership to Finland and Sweden, two Partnership for Peace countries with a history of avoiding military alignment. Both countries have welcomed greater military cooperation with NATO following Russia’s intervention in Ukraine. (Nordic peers Denmark, Iceland, and Norway are charter NATO members.)


Resources Up

This policy brief from the European Leadership Network (PDF) provides a preliminary analysis of the 2015 budget decisions in selected NATO member states.

This CFR Backgrounder surveys Russia's military buildup and the potential consequences for Eurasian security and politics.

This video from NATO Review magazine examines the roots of the current friction between Russia and the alliance.

In Opening NATO's Door, Ronald D. Asmus bears witness to the politics behind alliance enlargement after the fall of the Soviet Union.

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