In 1961, Charles de Gaulle, the French president, asked his American counterpart John F Kennedy if the United States ‘would be ready to trade New York for Paris’. His pointed question was about whether the US would be prepared to defend its European NATO allies, thereby risking a nuclear attack by the Soviet Union which had acquired intercontinental ballistic missiles capable of reaching the US mainland in 30 minutes.
No response from Kennedy would have convinced the French leader that such a sacrifice would be made. The year before France had carried out its first nuclear weapon test to become the fourth nuclear-armed power, independent of the United States.
Six decades on similar doubts are resurfacing among leaders, strategists and electorates from Warsaw to Seoul, from Canberra to Ottawa. This time, however, the cause isn’t the acquisition of a new weapon system by Washington’s adversaries, but a change in America’s temperament and approach to alliances. The result is the prospect of an alarming new nuclear age in which, after nearly 40 years of reductions in global stockpiles of nuclear weapons, their numbers may be increasing once again.
Rogue states
In recent decades, fears of proliferation have focused on non-aligned states, such as India and Pakistan, or so-called ‘rogue’ regimes such as Iran or North Korea. Today, strikingly, it is American allies who are beginning to consider nuclear weapons of their own. That is because Donald Trump’s bid to remake America’s approach to its alliances includes the possibility that Washington may also abandon the longstanding principle of nuclear nonproliferation that has been central to its grand strategy since the mid-1960s.
When China became the fifth country to join the nuclear club in 1964, President Lyndon B Johnson convened a task force to study the consequences of nuclear proliferation. The committee, led by Roswell Gilpatric, reported back in 1965 with a stark conclusion: ‘Preventing the further spread of nuclear weapons is clearly in the national interest despite the difficult decisions that will be required.’
For the remainder of the Cold War, America tackled these ‘difficult decisions’ by persuading its allies that nuclear weapons of their own would be costly and risky – better to accept American protection instead. This meant placing US nuclear weapons on allied territory, certifying allied pilots to deliver them and creating new forums for consultation with allies on nuclear policy. When South Korea and Taiwan tried to go nuclear in the 1970s and 1980s, Washington applied decisive pressure to ensure they remained non-nuclear.
The US also sought to persuade the Soviet Union to collaborate on promoting a global system of nuclear nonproliferation, leading to the Treaty on the Nonproliferation of Nuclear Weapons, or NPT. It came into force in 1970 and, with 191 parties, it is among the most effective arms control arrangements in history.
Goodbye nuclear optimism
With the end of the Cold War in 1991, a second nuclear age dawned. The Russian Federation inherited the nuclear stockpile of the Soviet Union. America unilaterally and through arms control with Russia reduced the size of its nuclear arsenal, drawing back its nuclear weapons deployed to Asia and nearly all of its nuclear weapons deployed to Europe.
The 1990s, despite crises in South Asia and the Korean Peninsula, was a moment of nuclear optimism. Global governance on nonproliferation and nuclear disarmament grew stronger as the NPT was extended indefinitely and a global Comprehensive Nuclear Test-Ban Treaty agreed. Between the mid-1980s and 2000, the global stockpile of nuclear warheads fell from 70,000 to around 12,500, where it remains today.
That optimism is now a distant memory. Relations between Russia and the West are the worst they have been since the Cold War. Moscow’s full-scale invasion of Ukraine has been backed by overt and covert nuclear threats. After February 2026, when the 2010 New START strategic arms treaty between the US and Russia expires, the two countries will be without limits on the size of their nuclear arsenals for the first time in more than 50 years.
Meanwhile, China is rapidly expanding its nuclear forces, aiming for an arsenal of up to 1,500 warheads, bringing it closer to parity with the US and Russia, which each possesses about 5,000 warheads. Arms control theorists continue to struggle to devise a plausible pathway to an equilibrium between Russia, America and China. A three-way arms race is likely.
The deterrence problem
In this third nuclear age, new and complex dynamics are emerging. North Korea is no longer a nonproliferation challenge, but a nuclear deterrence problem for the US. In April and May, India and Pakistan engaged in the most serious military exchange since their arrival as nuclear powers in 1998. Moreover, novel technologies, from cyber-weapons to artificial intelligence, have increased anxieties about new pathways to nuclear war.
For American allies in Europe and East Asia, these developments are leading to greater insecurity and anxiety. The world is more dangerous and, with it, the threat of conventional war between states and an ensuing nuclear conflict is higher than it has been in decades. An America that was faithful to the essential insight of the Gilpatric committee would respond to this with reassurance. Instead, at the Munich Security Conference in February, US Vice President JD Vance excoriated European values, suggesting a US administration that is uninterested in Europe’s sovereignty – perhaps even its survival. His speech echoed what Trump has long stated: that America’s allies have been taking Washington for a ride for decades, were undeserving of its protection and must ‘pay their fair share’.
At question now is America’s commitment to NATO and the Article 5 collective defence clause, including its willingness to maintain the US nuclear umbrella under which member states have sheltered. The ambivalence is underscored by Trump’s inconsistent pronouncements. Campaigning in the run-up to his first presidency, Trump suggested South Korea and Japan might need to acquire nuclear weapons, for instance. At other times he has termed the spread of nuclear weapons the ‘single biggest threat’ to the world.
An American military aide carries a briefcase known as the ‘football’ containing emergency nuclear weapon codes across the White House lawn. Photo: Saul Loeb/ AFP via Getty Images.
Like his predecessors, Trump appears to believe that American adversaries such as Iran should remain non-nuclear. Yet in 2018 during his first presidential term, Trump chose to withdraw the US from the 2015 Joint Comprehensive Plan of Action which limited Iran’s nuclear weapons programme in exchange for sanctions relief. Iran is now believed to be closer than ever to developing its first nuclear weapon.
Trump contradictions
At the same time, Trump has shown an interest in deep arms reductions with Russia and China, an objective that would become far more difficult should American ambivalence towards its allies push them to acquire nuclear weapons. The prospect of a nuclear-armed Germany, Poland, South Korea and Japan may be unlikely – but should it take shape and impinge upon the security interests of Moscow and Beijing, arms control and reduction among the major powers would be nigh-on impossible.
For America’s allies, these contradictions may be beside the point. America can no longer be treated as the cornerstone of their national defence, and relying on Washington for deterrence may be more of a liability than an asset. Trump’s predecessor, Joe Biden, failed to persuade allies that their experience in Trump’s first term was an aberration and that the US was fundamentally ready to ‘repair our alliances and engage with the world once again’.
With Trump’s re-election, allies are starting to take matters into their own hands. European spending on national defence has spiked in the first months of 2025 and the continent’s two nuclear powers, Britain and France, are exploring ways to reassure European allies in order to prevent uncontrolled proliferation.
It is clear that the world can no longer take for granted longstanding principles of US grand strategy when it comes to nuclear weapons. The load-bearing pillar of American leadership in the global nuclear order is crumbling. But there are still options to avert the worst outcomes. First, Paris and London should, as a matter of urgency, seek to study the feasibility of erecting a new security architecture for Europe, built on the establishment of a new extended deterrence that incorporates their own nuclear capabilities. This is easier said than done. Neither has seriously contemplated operating in a world without US support. Also, France’s deterrent is more independent than Britain’s which relies on cooperation with the US.
Yet creative thinking and new investments – including in nonstrategic nuclear options – can show the rest of the continent that nuclear deterrence without America is not a lost cause, particularly when paired with investments by other European countries in substantial new non-nuclear defence capabilities, including long-range missiles and drones.