Five Facts on NATO Expansion

The Big InsightThough NATO has expanded eastward since the end of the Cold War, it has rarely been called upon to fight — and only once on behalf of one of its member states after attack.

1. NATO was founded by 12 nations in 1949 and today has 30 member states, including three former Soviet republics and 11 former Eastern Bloc nations.

At the end of the Cold War, NATO began expanding eastward. While then-Secretary of State Secretary of State James Baker told Soviet leader Mikhail Gorbachev in February 1990 that “there would be no extension of NATO’s jurisdiction for forces of NATO one inch to the east,” some analysts say this referred solely to the state of affairs while the Soviet Union still existed. Gorbachev himself later said, “The topic of ‘NATO expansion’ was never discussed. It was not raised in those years.”

Still, the expansion has been a sore point in U.S.-Russian relations. In 1998, former U.S. Ambassador to the Soviet Union George Kennan warned, “I think the Russians will gradually react quite adversely and it will affect their policies. I think it is a tragic mistake. … We have signed up to protect a whole series of countries, even though we have neither the resources nor the intention to do so in any serious way.”

2. Article 5 of the NATO treaty, which states that an attack on one member of NATO is an attack on all of its members, has been invoked just once.

NATO invoked Article 5 on September 12, 2001, the day after Al Qaeda attacked the United States. The article directly states that “an armed attack against one or more of them…shall be considered an attack on them all,” with no differentiation between an attack on a NATO ally and on a member state’s own territory.

3. NATO currently recognizes three nations — Bosnia and Herzegovina, Georgia, and Ukraine — as under consideration for membership.

These countries partner with NATO in certain areas of mutual interest but are not party to the formal Article 5 defense pact. A nonbinding referendum on NATO membership in Georgia in 2008 passed with 77% in support, but Russian Foreign Minister Sergey Lavrov has warned against it, stating that “NATO approaching our borders is a threat to Russia.” Similarly, polls show broad support for NATO membership in Bosnia and Herzegovina, but opposition in the pro-Russian Republika Srpska region, which makes up about one-third of the population.

A December 2021 poll found that 54% of Ukrainians would vote to join NATO if a referendum were held.

4. NATO has undertaken eight military actions, all since 1990.

Even though NATO was founded as a defense against the Soviet Union, the alliance did not undertake any military operations during the Cold War. Since 1990, NATO has engaged in two actions related to the first Gulf War, two related to the conflict in the former Yugoslavia, and conflicts in Afghanistan, Iraq, Somalia, and Libya.

5. The combined military spending of NATO states makes up 57% of global military spending.

In 2014, NATO members agreed to each spend at least two percent of their GDP on defense by 2024. However, only one-third of its members currently meet that target: Greece (3.82%), the United States (3.52%), Croatia (2.79%), the United Kingdom (2.29%), Estonia (2.28%), Latvia (2.27%), Poland (2.1%), Lithuania (2.03%), Romania (2.02%), and France (2.01%).


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