Is NATO going nuclear?

At a NATO summit in late June, British Prime Minister Keir Starmer announced his country’s intent to purchase a dozen F-35A fighter jets capable of carrying nuclear bombs. Although the planes will belong to the United Kingdom, the weapons will belong to the United States under a “nuclear sharing” arrangement. Like many NATO members, Britain relies on U.S. security guarantees in the event of a nuclear attack. But several countries in the 32-nation alliance have hinted at developing their nuclear arsenals apart from U.S. involvement.

What countries have atomic weapons? Nine countries have nuclear weapons, but Russia and the United States control nearly 90% of the world’s approximately 12,000 warheads. The Arms Control Association estimated in January that Russia holds some 5,580 warheads, compared with roughly 5,225 owned by the U.S. China has the third-highest collection with around 600 nukes. France, the U.K., India, Pakistan, Israel, and North Korea also have nuclear stockpiles. Five additional countries including Turkey host U.S.-owned weapons. During the 1980s, the global stockpile of warheads peaked at around 70,000.

What were the recent Israeli and U.S. airstrikes on Iran all about? The strikes were meant to deter the country from producing material for a nuclear weapon, a development some experts speculated was only a few months away. A leaked preliminary U.S. intelligence report claimed the strikes delayed Iran’s progress by less than six months, but Pentagon officials insist it will take Iran’s program up to two years to recuperate.

Why haven’t more countries developed atomic weapons? In 1968, during the height of the Cold War, the United Nations adopted the Nuclear Non-Proliferation Treaty to prevent the spread of nuclear arms. Since then, 191 countries, including five nuclear ones, have signed the treaty.

What’s the U.S. role in nuclear nonproliferation? The United States extends security guarantees to NATO members that don’t possess nuclear weapons (along with France and the U.K.) and to the non-NATO countries of Japan, Australia, and South Korea. These security guarantees form the basis of a “nuclear umbrella,” a pledge to retaliate if any country under the umbrella is attacked with nuclear weapons.

Which NATO members want independent nuclear protection? In March, French President Emmanuel Macron proposed using France’s nuclear arsenal to protect nearby countries—an offer Polish Prime Minister Donald Tusk said he was entertaining. German politician Jens Spahn recently told the German newspaper Welt that Germany should have a “debate about an independent European nuclear umbrella.” Still, nonproliferation agreements may prove a significant hurdle for U.S. allies.

What’s behind the push for allied-owned nukes? The Russian war on Ukraine since 2022 has set Europe on edge. U.S. President Donald Trump has been noncommittal about continuing to fund Ukraine’s defense effort, and he’s simultaneously pressured NATO members to boost their own defense spending. As a result, some Europeans have grown skeptical of U.S. loyalty in the event of a nuclear attack. “We need to be cognizant that this world order and peace is underpinned by American nuclear weapons,” argues Andrea Stricker, a research fellow with the Foundation for Defense of Democracies. “We need to ensure that our European and Asian allies are comfortable with our word that we would intervene if they were attacked.”