It is no coincidence that Prime Minister Donald Tusk of Poland openly raised the possibility that his country may need to arm itself with nuclear weapons. Both major parties in South Korea are doing the same. This is a response to what is happening in Washington, where the Trump administration is renovating America’s post-World War II grand strategy, tossing aside hard-built alliances, norms on global trade, and much else. Coercive tariff threats, territorial expansionist rhetoric, and expressions of trans-national far-right political solidarity are in. Liberal values and support for what American presidents once described as a “rules-based order” are out. Trump has openly said that allies can no longer reliably count on America, or its nuclear forces, as their ultimate security guarantor. Tusk’s willingness to consider a nuclear arsenal should therefore not be surprising. Indeed, other American allies around the world are considering the same, as well as alternative nuclear-sharing agreements that once seemed fanciful. This will be the potential price of gutting American extended deterrence commitments, the most successful nonproliferation tool the United States has had for three-quarters of a century.
Preventing the spread of nuclear weapons, to friend and foe alike, has been a core bipartisan pillar of American foreign policy for decades. Perhaps some Trump administration officials greeted Tusk’s announcement warmly. Indeed, it is no secret that President Donald Trump himself and some of his prominent advisors have shrugged at the prospect of nuclear proliferation, despite the president’s open discomfort with nuclear weapons and his musings about nuclear disarmament as a part of a deal with Russia and China. To be sure, proliferation to American allies might mean big savings on the peacetime costs of forward deployed troops and avoiding entanglement in crises in far-flung theaters.
However, welcoming more nuclear-armed countries, even if they are friends of the United States, threatens core American interests. Trump’s “America First” instincts rely on and relish unrestrained American power and primacy. As such, Trump may find that the longstanding American interest in nonproliferation actually serves his worldview rather than compromises it. Allies with nuclear weapons will complicate America’s ability to exercise its power. They’re more likely to chart independent, possibly oppositional political and economic policies. And perhaps counter-intuitively, they might make it more likely that the United States gets dragged into a nuclear crisis or war.
The Real Costs of Nonproliferation to American Power
While U.S. policy makers in the post-Cold War decades focused global nonproliferation attention on countries other than allies — notably India, Pakistan, North Korea, and Iran — the looming shifts in a U.S. grand strategy that may bring America home have, in recent years, put the focus on allies. Until now these allies, including South Korea, Japan, Germany, and Poland, have been able to forswear nuclear weapons because they were ultimately shielded by the American nuclear umbrella.
Early in the Cold War, following the advent of nuclear weapons, the United States did not intuitively grasp the reasons why nuclear proliferation to its friends would harm its interests. It was only in the early 1960s, after France sought a nuclear weapons capability to assert its independence from the United States and NATO’s nuclear deterrent mission, that Washington began to really introspect on the value of nonproliferation for its own interests.
The United States worked hard during the Cold War to prevent proliferation — not just by its adversaries but also its allies. A combination of security commitments, forward-positioning of U.S. conventional and nuclear weapons, and a lattice-work of dialogues, exercises, and information sharing agreements formed the heart of a U.S. strategy that “extended” deterrence to what is now more than 30 allies. Rendering this credible was a constant effort for the United States. This was especially true at the height of the Cold War and has become more pertinent recently amid growing threat perceptions in Europe and Northeast Asia alike.
This strategy, backed by a large U.S. nuclear arsenal, a flexible nuclear posture, and an explicit political commitment to extend these tools to the defense of Europe, let the allies safely focus on other ventures. European democracies focused on economic growth and trade and the well-being of their citizens, enabled by U.S. aid. In turn, these actions stimulated the U.S. economy, creating a massive long-term marketplace for U.S. producers. The commitments Washington undertook made nuclear weapons acquisition by allies and partners unnecessary, and rather than pursuing expensive, dangerous nuclear weapons programs, allies agreed to maintain a non-nuclear status and built wealth instead.
The origins of what became an enduring strategic preference for nonproliferation at the time had little to do with high-minded ideas about liberal internationalism, political solidarity with democracies, or values. It was good for American security interests. The spread of nuclear weapons, U.S. policymakers observed, would only serve to limit America’s freedom of action in the international system and endanger U.S. interests. Simply put: Nuclear proliferation to both allies and adversaries dilutes the privileges of power the United States enjoys.
‘America First’ Needs Nonproliferation
In the contemporary context, this quite literally means that pursuing a grand strategy that seeks to place ‘America First’ at the heart of U.S. statecraft should prize nonproliferation. Most importantly, allied proliferation complicates America’s ability to exercise its hard power, limiting the privileges of primacy that Trump so relishes.
First, in practical terms, allies today that consider building their own nuclear arsenals need to contend with the strategic and technical barriers to actually doing so. Ukraine, Poland, South Korea, and even Taiwan all would face the potential of an explicit renunciation of U.S. protection or assurances if they chose to pursue nuclear weapons. While some in these states may argue this is today’s status quo with the Trump administration’s approach to alliances, they would face the problem of vulnerability to attack as they sought to build the bomb. Reprocessing and enrichment facilities will be hardly invulnerable to attack, and their adversaries — Russia, China, and North Korea — will have ample incentive to consider sabotage, conventional air strikes, or worse. Russian, Chinese, or North Korean attempts to kill our proliferation-curious allies to stop them from getting there could drag us into a major conflict, as they would certainly threaten the stability of the global economy and thus American interests.
Second, even with friendly countries that might successfully proliferate, the actions they take after acquiring nuclear weapons may force Washington to intervene in crises or wars against its own interests. For instance, an ally may force a U.S. president to step in and prevent dangerous nuclear signaling or use, as has been the case in the past with the United Kingdom, France, and Israel in 1956; Israel in 1973; and India and Pakistan after 1998.
A newly emboldened but still weaker nuclear-armed ally or partner may try to provoke a major U.S. adversary, pulling the United States into a crisis as a mediator, or worse. With more nuclear-armed states, the intersection of crises that may implicate U.S. interests with nuclear weapons uncontrolled by Washington becomes far more likely. In a world of reduced U.S. influence on multiple, skittish new nuclear decision-making centers in Asia, the Middle East, Africa, or elsewhere, states are less likely to consider Washington’s opinion before engaging in nuclear threat-making — or use — to address local grievances or right historical wrongs.
This would hardly serve an ‘America First’ world. The potential for metastasizing nuclear crises assuredly contradict the goal of the “strategic prioritization” that former and incoming officials support.
In addition to diminishing American power, further proliferation anywhere — especially by prosperous, democratic allies of the United States, like South Korea — is likely to beget further proliferation everywhere. While some U.S. officials may be comfortable with a nuclear South Korea, they should ask whether they are comfortable with all that may follow in total — such as Japan, Taiwan, Poland, Saudi Arabia, all supporters of today’s nonproliferation regime. Should this dam break, the United States’ relative power and influence stands to decline. And Trump’s dreams of a denuclearization pact with Russia and China will be completely out of reach in a world where multiple new nuclear aspirants emerge. Keeping ‘America First’ in that world becomes a lot more challenging. Keeping nuclear use from occurring, and potentially embroiling the United States, an ally, or other economic partner in a conflict, becomes much more unpredictable.
The history of nuclear proliferation suggests that any decisions to shelter or encourage allied proliferation are likely to be permanent. With the exception of South Africa, no other state — not even Ukraine, which never had control over the weapons on its territory — has ever relinquished its nuclear weapons. Despite the remarkable success of the United States in leading nonproliferation efforts worldwide, the proliferation genie does not easily reenter its bottle. The acquisition of nuclear weapons is a lasting mark on international politics, and America’s freedom to maneuver, even if by “friendly states.”
Compared to these potential costs, the administration should tread carefully as it seeks to revise longstanding compacts with its treaty allies around the world. While Trump reels at the peacetime costs of sustaining forward-deployed conventional forces in Europe and Asia, seeing them as evidence of the United States being taken for a ride, the alternatives could be far more costly to the United States. Unleashing a cascade of nuclear proliferation, or rebuilding American economic strength in the aftermath of nuclear conflicts, would be far more expensive than sustaining the U.S. extended deterrence approach.
The surest way for the “crazy” power of nuclear weapons to boomerang back at the United States — constraining our freedom of action and potentially chain-ganging us into conflicts we seek to avoid — is for Washington to actively dismantle the extended nuclear deterrence architecture it so carefully crafted over three-quarters of a century, which managed to keep new allies from getting the bomb. In addition to reinstalling the software of extended deterrence, in order to prevent allied proliferation, the United States may have to make adjustments to the size or composition of its own deployed nuclear force posture. This will ensure that its hardware remains credible for deterrence, as well as assurance — some degree of vertical proliferation may be necessary to stanch the threat of horizontal proliferation, an oft lost point.
The post-Cold War conflation of nuclear nonproliferation with the so-called liberal order was understandable given the geopolitical context of the 1990s, but for the United States, is largely ahistorical. If Trump wants to pursue a grand strategic project with the goal of keeping ‘America First’, nuclear nonproliferation — not just by adversaries but also by allies — is an essential pillar.
Ankit Panda is the Stanton senior fellow in the Nuclear Policy Program at the Carnegie Endowment for International Peace and the host of Thinking the Unthinkable for War on the Rocks.
Vipin Narang is the Frank Stanton professor of nuclear security and political science at the Massachusetts Institute of Technology. He served as acting assistant secretary of defense responsible for nuclear deterrence policy during the Biden administration.
Pranay Vaddi is the senior nuclear fellow at the Center for Nuclear Security Policy at the Massachusetts Institute of Technology. He recently served as President Joe Biden’s senior director for arms control, disarmament, and nonproliferation on the National Security Council.
Image: Lisa Simunaci via U.S. Department of Defense
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