Spain, NATO, and the Limits of Alliance Power
A dispute between Washington and Madrid has exposed a structural weakness at the heart of NATO. Spain has resisted the alliance’s new defense-spending target, refused to let its jointly operated bases support American strikes against Iran, and restricted the use of its airspace by aircraft involved in the operation. In response, President Donald Trump has threatened economic retaliation and suggested that Spain could be removed from NATO.
The political confrontation is serious, but the legal question is even more consequential. NATO’s founding treaty explains how a country can join and how it can leave voluntarily. It does not establish a straightforward procedure for suspending or expelling a member against its will.
A dispute that began with defense spending
The conflict predates the war with Iran. NATO members agreed on a long-term goal under which they would devote 5 percent of national economic output to defense and security-related priorities by 2035. At least 3.5 percent would go directly to armed forces, personnel, equipment, and military capabilities. The remaining 1.5 percent could cover areas such as critical infrastructure, cybersecurity, and civilian preparedness.
Spain was the most prominent opponent of that target. Prime Minister Pedro Sánchez argued that Madrid could provide the military capabilities NATO requires with about 2.1 percent of its economic output. Reaching 5 percent, he warned, would require steep tax increases or cuts to pensions, education, and social programs.
Washington interpreted Spain’s position differently. From the American perspective, a country that spends substantially less than its allies cannot expect the same level of protection while leaving others to carry a larger share of the burden. That disagreement turned a debate about budgets into a test of political loyalty.
Why Rota and Morón matter
The strategic importance of Spain is clearest in the country’s south, where the United States operates from two major facilities under bilateral agreements.
Naval Station Rota sits near the Strait of Gibraltar, the narrow maritime gateway between the Atlantic Ocean and the Mediterranean Sea. Its location allows American and allied forces to move ships and personnel toward Europe, North Africa, and the Middle East. The port also supports the supply, maintenance, and arming of vessels, while American destroyers are stationed there on a permanent basis.
Morón Air Base, southeast of Seville, has a long runway capable of handling heavy transport aircraft, tankers, and strategic bombers. It provides a useful platform for operations across the Mediterranean, Africa, and the Middle East.
Neither installation is American sovereign territory. They are Spanish military bases where American forces operate under an agreement between Madrid and Washington. Spanish authorities retain sovereignty, and Spain can impose limits on how the facilities are used. That distinction became decisive when Madrid rejected the use of Rota and Morón for attacks on Iranian targets.
The bases are older than Spain’s NATO membership
The American presence in Spain began during the Cold War, before Spain joined NATO. In 1953, Washington and the government of Francisco Franco signed an agreement that provided Spain with economic and military support while granting the United States access to several Spanish bases.
That history creates an important legal separation. The American military presence does not rest primarily on NATO membership; it rests on a bilateral arrangement. Spain could leave NATO without automatically ending the basing agreement, and it could remain in NATO while restricting American use of specific facilities. The alliance dispute and the basing dispute are connected politically, but they are not the same legal matter.
Spain joined NATO in 1982, after the transition away from Franco’s dictatorship. Membership was controversial at home, and a 1986 referendum approving continued participation came with conditions, including limits on integration into NATO’s military command structure and restrictions on the deployment of nuclear weapons. Spain eventually joined the integrated military command structure in 1999.
That background helps explain Madrid’s longstanding view that alliance membership must coexist with national sovereignty and an independent foreign policy. Spain has never treated participation as an obligation to support every military decision made in Washington.
What the spending figures do—and do not—show
Trump’s criticism often frames the issue as if Spain owes money directly to NATO or the United States. That is misleading. Defense-spending targets generally refer to money each country spends within its own national system on forces, equipment, infrastructure, and security capabilities.
Spain has historically ranked near the bottom of NATO members by the share of its economy devoted to defense. Its reported level was about 1.28 percent in 2024, before Madrid increased spending sharply and moved toward the 2 percent benchmark in 2025. Spanish officials argue that percentages alone do not measure military value. They point to ships, aircraft, air-defense systems, personnel, and contributions to joint missions.
That argument collides with Washington’s increasingly strict focus on a common percentage. Madrid emphasizes capabilities and concrete deployments; the United States emphasizes predictable financial commitments. Both approaches reflect genuine concerns, but they measure alliance contribution in fundamentally different ways.
The Iran war turned disagreement into confrontation
The dispute escalated when the United States and Israel launched extensive attacks against Iranian targets. Washington sought to use the facilities at Rota and Morón in support of the operation. Spain refused permission, with Sánchez describing the war as illegal, dangerous, and unsupported by international law.
Spain then closed its airspace to American aircraft participating in the operation. Trump responded with threats to halt trade with Spain and argued that the United States should be able to use the bases without Madrid’s approval. American officials accused Spain of placing the lives of U.S. personnel at risk by obstructing the operation.
Madrid maintained that an alliance does not require a member to support every war conducted by another ally. For Spain, refusing assistance in what it considered an unlawful conflict was an exercise of sovereignty, not a rejection of collective defense.
Can NATO suspend or expel Spain?
The North Atlantic Treaty contains only 14 articles. Article 10 governs the admission of new European states, while Article 13 allows a member to leave after giving formal notice, with withdrawal taking effect one year later.
There is no equivalent article authorizing the other members to expel a country. Nor does the treaty establish a normal procedure for suspending a member from NATO’s political work. NATO decisions also generally depend on consensus rather than majority voting, making a unilateral American removal order legally implausible.
The United States is the treaty’s depositary, meaning it performs an administrative role for the agreement. That status does not give Washington a special power to eject another member. On the treaty’s face, Spain remains a member unless it chooses to withdraw or the allies devise an entirely new political and legal arrangement.
Membership could be weakened without formal expulsion
The absence of an expulsion mechanism does not mean the United States is powerless. Washington could reduce bilateral military cooperation, withdraw troops and aircraft, limit intelligence sharing, restrict arms transfers, or apply economic pressure. Other allies could exclude Madrid from informal consultations, joint projects, or selected forms of cooperation.
Those steps would not remove Spain from NATO on paper. They could, however, leave it politically and militarily isolated in practice. A member can retain its legal status while losing influence, access, and trust.
The dependence also runs in both directions. Spain relies on American military capabilities, weapons, and leadership within NATO. The United States, meanwhile, benefits from Spain’s geography. Rota and Morón are not irreplaceable, since Washington has facilities in countries including Italy, Germany, Greece, and Turkey. But losing Spanish access would make many operations longer, more expensive, and more complicated.
What the crisis means for Article 5
Spain is unlikely to be formally expelled because NATO has no ordinary mechanism for doing so. The more important issue is the damage caused by treating alliance membership as conditional political obedience.
Collective defense depends on more than treaty language. It depends on confidence that allies will support one another when threatened, while also respecting each other’s legal authority and political limits. If Washington makes security guarantees appear dependent on support for American wars or compliance with a fixed spending target, trust will suffer. If Madrid denies access whenever a mission conflicts with its own interpretation of international law, Washington will also see the limits of its influence.
The confrontation therefore reveals a difficult balance. NATO must persuade members to invest adequately in common defense, but it also has to accommodate sovereign governments that may reject a particular military operation. Spain’s position shows that alliance solidarity and national control are not identical concepts—and that the tension between them can become more dangerous than any formal withdrawal.
