What NATO is
The North Atlantic Treaty Organization is a military alliance formed in 1949 by the United States, Canada and 10 European nations in the early years of the Cold War. It has since grown to 32 members, most recently with Finland joining in 2023 and Sweden in 2024 — the first additions in more than a decade, following Russia's 2022 invasion of Ukraine.
Article 5 and how the alliance works
The treaty's core provision, Article 5, states that an armed attack against one member is considered an attack against all. The clause does not require a specific military response; each member decides what action to take. It has been invoked only once in NATO's history — by the United States after the September 11, 2001 attacks, which led to allied participation in the war in Afghanistan.
Who pays what
NATO members agreed in 2014 to spend at least 2% of their gross domestic product on defense. According to NATO's own figures, 23 of 32 members met the target in 2024, up from 6 in 2021. The United States is the alliance's largest contributor: estimates of the U.S. share of combined NATO defense spending range from roughly 67% to 71%, depending on how indirect costs such as overseas deployments are counted.
The case for staying
Supporters argue NATO has helped prevent major-power war in Europe for 75 years and provides the United States with forward bases, intelligence-sharing, and a network of allies that would be difficult to replicate. They contend that collective deterrence is achieved at relatively modest cost — U.S. defense spending is driven largely by global commitments, not NATO alone — and that recent increases in European spending show the alliance adapting to new threats.
The case for leaving or restructuring
Critics argue that European members have long under-invested in their own defense, leaving the U.S. to shoulder a disproportionate share. Some contend that NATO's eastward expansion after the Cold War has provoked rather than deterred Russia, contributing to conflicts in Georgia and Ukraine. Others favor remaining in the alliance but renegotiating terms to push allies toward higher spending or a larger share of operational costs.
What withdrawal would involve
Under the treaty, a member may withdraw one year after notifying the U.S. government, which serves as depositary. In 2023, Congress passed a provision requiring Senate approval or an act of Congress before any president can withdraw the U.S. from NATO — though the constitutional reach of that law has not been tested in court. No member has ever left the alliance.
What to weigh as a voter
Key questions include whether the deterrent value of the alliance outweighs its costs, whether the U.S. should condition its commitments on allied spending levels, and how membership shapes relations with Russia and China. Reasonable people disagree on each of these, and the trade-offs depend on judgments about future threats that cannot be known with certainty.