What is NATO and why was it formed?
The alliance binds 32 European and North American countries together in a common-defense agreement.
NATO is a military alliance composed of 32 member countries from North America and Europe. The organization was formed in 1949 as a collective defense organization to counter the Soviet Union during the Cold War. The United States has been a member of NATO since 1949.
Its primary purpose today is to promote security and defense cooperation among its members while also serving as a forum for consultation and coordination on political and security issues.
Which countries are in NATO and how do countries join?
Any European state may join NATO after receiving a unanimous invitation from its NATO members. Since 1949, the alliance has grown from 12 to 32 members. Both Finland and Sweden were invited to join NATO at the Madrid Summit on June 29, 2022. Finland became a member on April 4, 2023, and Sweden followed on March 7, 2024.
As of April 8, 2026, NATO's membership includes (in alphabetical order):
- Albania
- Belgium
- Bulgaria
- Canada
- Croatia
- Czechia
- Denmark
- Estonia
- Finland
- France
- Germany
- Greece
- Hungary
- Iceland
- Italy
- Latvia
- Lithuania
- Luxembourg
- Montenegro
- North Macedonia
- Norway
- Poland
- Portugal
- Romania
- Slovakia
- Spain
- Sweden
- The Netherlands
- Türkiye
- United Kingdom
- United States
Sweden joined NATO on March 7, 2024, bringing total membership to 32 countries.
NATO member countries by year of admission, April 2026
Which countries want to join NATO?
Three countries have declared a desire to join the alliance: Bosnia and Herzegovina, Georgia, and Ukraine. Bosnia-Herzegovina has participated in a NATO program for aspiring members since 2010.
NATO members agreed in 2008 that Georgia and Ukraine would join the alliance but did not specify when. Their admission depends on fulfilling certain criteria, including defense reforms. Both countries are currently facing Russian interference, ranging from occupation to active conflict.
NATO's 30 European member countries admission dates span from 1949–2024
Map of European NATO countries by year of admission
How much does it cost to be in NATO?
NATO countries have two funding obligations. The first is contributions to the common fund, which is direct funding for NATO. The second is a commitment to spend at least 2% of a country’s Gross Domestic Product (GDP) on national defense or military spending, which is considered indirect funding.
At the 2025 NATO summit, the allies agreed to increase defense spending to 5% of GDP by 2035.
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The common fund (direct funding)
Each member contributes to a common fund based on the size of its overall economy.
NATO’s common fund budget—up to $6.2 billion in 2026—supports the NATO Security Investment Program (NSIP), the Military Budget, and the Civil Budget. These funds support collective military infrastructure, including defense, readiness and interoperability, digital and cyber capabilities, and other administrative costs.
The US is projected to cover roughly 15% of NATO’s 2026 budget, or around $933 million. Although NATO benefits from US funding, the US also benefits from operating within—and having access to—military bases in foreign countries, as well as from enabling U.S. contractors to bid for and win NATO projects.
The 5% rule (indirect funding)
In addition to direct funding, each country is expected to invest a percentage of its national GDP in its own national defense or military spending. Although this is not an explicit requirement of membership, it is viewed as a measure of a country’s commitment to NATO and to common defense efforts.
At the 2025 NATO summit in The Hague, Netherlands, the allies agreed to increase defense spending to 5% of GDP by 2035, up from the previous target of 2%.
In FY 2025, 31 NATO members met the target of spending at least 2% of their GDP on defense, based on estimates. Poland spent the highest percentage on defense at 4.4%, followed by Lithuania at 4.0%.
The US is the only NATO member to report a decrease in military spending since 2014.
Defense expenditures as a percent of total GDP, FY 2014 and FY 2025
Historically, the US spends more on domestic defense than the rest of NATO. After adjusting for inflation, total defense spending for non-US NATO countries was $608.0 billion in 2025.
In the same year, US total domestic defense spending was $980.0 billion.
The US spends more on defense than all other NATO members combined.
Total defense spending in US dollars, FY 2014–2025
What is Article V?
Article V is a crucial provision within NATO’s founding treaty that states that an attack on one member country will be considered an attack on all member countries. It signifies the collective defense commitment among NATO members. When one member is attacked, all other NATO countries are expected to assist allies, including with military force.
NATO invoked Article V for the first and only time to join the US in the war in Afghanistan after the September 11, 2001, terrorist attack.
The US Congress still needs to approve the request to go to war even if Article V of NATO is invoked. Therefore, provisions within the NATO treaty do not supersede the power of the US Constitution.
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