What is NATO?
NATO – the North Atlantic Treaty Organization – has been an anchor of stability in the world for more than 70 years.
- NATO is a political and military alliance. Established in 1949, NATO provides a permanent structure for its 32 member countries to consult and cooperate on defense and security-related issues. It’s not just about military power – though members have deployed together, including after the United States was attacked on 9/11. NATO centers around regular consultations that enable intelligence sharing, build trust, solve problems, and help prevent crises from spiraling.
- NATO nations share democratic values. The strength of the alliance is that members have made a conscious choice to stand together on a shared set of principles: democratic governance, individual freedom, open economies, and a sense of solidarity. These democratic values underpin the alliance’s credibility, stability, and resilience.
- NATO is all about deterrence. It’s a defensive alliance. No NATO nation stands alone if attacked. Both allies and adversaries understand this pledge, codified in Article 5 of the alliance’s foundational 1949 Washington Treaty. The clause has been invoked exactly once in NATO’s history – in support of the United States.
- NATO is more than numbers. For the United States, NATO is about having a ready-made network of capable partners. Its real advantage is interoperability. NATO’s real advantage is interoperability. NATO forces train together; share advanced tactics, equipment, and, often, weapons platforms; and consult and plan together. NATO countries have spent decades building habits of cooperation and networks of trust.
NATO is a voluntary alliance that has grown and adapted to events throughout its history.
- Twelve nations formed NATO in 1949: Belgium, Canada, Denmark, France, Iceland, Italy, Luxembourg, Netherlands, Norway, Portugal, the United Kingdom, and the United States. Through NATO’s “Open Door” policy, 20 nations have joined through subsequent unanimous decisions of the alliance as geopolitical events shifted the transatlantic landscape.
- In 1952, Greece and Turkey joined. This expanded NATO’s southern flank. The alliance added Germany in 1955 and Spain in 1982.
- After the end of the Cold War, new democracies sought NATO membership. Czechia (then the Czech Republic), Hungary, and Poland joined the alliance in 1999.
- NATO’s largest accession came in 2004. Bulgaria, Estonia, Latvia, Lithuania, Romania, Slovakia, and Slovenia became allies.
- Further expansion came over the next two decades. Albania and Croatia joined NATO in 2009, joined by Montenegro in 2017 and North Macedonia in 2020.
- NATO recently expanded its northern presence with the accession of long-time NATO partners Finland in 2023 and Sweden in 2024.
- Who can be members? Article 10 of the North Atlantic Treaty underscores that membership is 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” and that the invitation to join is made on the basis of consensus among all allies.
How is NATO funded?
- What is the “5%” commitment? Each NATO member is responsible for investing in its own military and capabilities. At the 2025 summit in the Netherlands, allies agreed to raise respective member-level defense investments by 2035 – individual country investments in their own defense, not direct cash transfers to NATO. These commitments are designed to build a stronger, more usable nation-based military capability across the alliance.
- What about common funding? NATO’s common-funded budgets, which pay for the NATO command structure, joint operations, and headquarters infrastructure, are based on an agreed cost-sharing formula derived from the gross national income of member countries. The common funding represents just 0.2% of total allied defense spending. The United States provides approximately 15% of the total common funding pool, again based on gross national income.
What has NATO done for the United States?
- Sept. 11: Article 5, NATO’s collective defense agreement, has only been invoked once in NATO’s 77-year history – in defense of the United States after the attacks of Sept. 11, 2001. In Operation Eagle Assist, NATO airborne-radar planes (AWACS) patrolled U.S. skies for almost eight months, the first time NATO forces had crossed the Atlantic to defend the United States.
- In Afghanistan, military forces from NATO allies, as well as NATO partner countries, deployed to Afghanistan with the United States to ensure that the country would not again become a safe haven for terrorism. From 2003 until 2014, NATO led ISAF, the U.N.-mandated International Security Assistance Force designed to support the then-Afghan government and build the capacity and professionalism of Afghan national security forces in the fight against international terrorism.
- After ISAF until the fall of Kabul in August 2021, NATO’s Resolute Support Mission, together with U.S. forces, maintained a “train, advise, and assist” antiterrorism role to support Afghan security forces and institutions to fight terrorism. Over 1,100 NATO allied forces were killed in these efforts, in addition to the more than 2,400 American service members who died.
- In Iraq, NATO allies joined the U.S.-led military command from 2004 to 2009 under the Multi-National Force-Iraq (MNF-I), often referred to as the coalition forces. Over 300 non-U.S. coalition members were killed in Iraq. From 2004 to 2011, the NATO Training Mission-Iraq trained the Iraqi Army and the Iraqi Police and then transitioned to NATO Mission Iraq in 2018 at the request of the government of Iraq to continue to help Iraq build transparent, inclusive, and effective Iraqi armed forces and security institutions.
