August 5, 2025

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Unraveling the Regime? How the 12-Day War Could Impact Nuclear Non-Proliferation

AP Photo/Alex Brandon

The June U.S. strikes on Iranian nuclear sites — Operation Midnight Hammer — mark a significant turning point in global nuclear proliferation. While Iran’s covert military nuclear activities were widely considered in breach of its non-proliferation obligations, the United States’ decision to strike its facilities — an act which contradicts the legal and institutional frameworks the U.S. helped create — risks undermining the credibility of that very system, weakening global efforts to prevent the spread of nuclear weapons.

In the aftermath of World War II, a number of states sought nuclear weapons to attain strategic autonomy and coercive leverage. However, widespread proliferation was averted through a deliberate U.S. strategy of deterring both nuclear-armed states from using their arsenals and dissuading non-nuclear states from pursuing them — primarily through the extended reach of the U.S. nuclear umbrella, which also served to protect its allies. In doing so, the United States reduced the incentives for all states to develop independent nuclear arsenals. This informal strategy was formalized with the Nuclear Non-Proliferation Treaty (NPT) in 1968, supported by additional treaties, such as nuclear-weapon-free zones, and organizations like the International Atomic Energy Agency (IAEA). This system largely held, with only Israel, Pakistan, India, and North Korea becoming nuclear powers outside the NPT framework. Yet the recent U.S. strikes may have dealt a significant blow to this system, which has primarily relied on the leadership and sustained commitment of the major nuclear powers—particularly the United States.

Even before the June strikes, the current global nuclear environment had become increasingly volatile. A bellicose Russia has resorted to nuclear saber-rattling to offset its battlefield setbacks in Ukraine, and a more assertive People’s Republic of China (PRC) has positioned itself for a potential future confrontation with the United States. For some countries, the future is one in which nuclear weapons are central to strategic planning, calling into question the international non-proliferation regime that has, until now, endured. Just last week, President Trump, responding to threats made on social media by former Russian president Dmitry Medvedev, stated that the U.S. had moved two nuclear submarines to “appropriate regions.” This is not the first time recently that nuclear threats have been issued. As Bob Woodward recounted in his book, War, the U.S. scrambled to urge Putin to eschew using tactical nuclear weapons in Ukraine to offset battlefield losses.

But it is the U.S. strike on Iran that may ultimately shatter this fragile system. By employing coercive force in nuclear-related matters, the U.S. risks undermining the legitimacy and authority of the non-proliferation regime, potentially normalizing a return to a more anarchic international order in which nuclear policy is dictated less by legal and diplomatic norms and more by power politics. This shift has likely already begun to compel various state actors — such as Iran or even U.S. allies like South Korea, Japan, Saudi Arabia, and Türkiye — to reassess their respective nuclear postures.

Since the 1990s, Iran has maintained a nuclear program characterized by alternating periods of cooperation with international agreements and phases of defiance and expansion. Analysts have estimated that, for several years, Iran has possessed the technical capacity to produce enough fissile material for a nuclear weapon within a matter of months. Despite this capability, Iran has refrained from fully weaponizing its program, the rationale being that a latent nuclear capability was sufficient to serve as a powerful geopolitical tool. This posture enabled Iran to alleviate its international isolation while maintaining a degree of strategic deterrence. Nuclear talks between the West and Iran prior to Operation Midnight Hammer — the 2015 Joint Comprehensive Plan of Action (JCPOA), and the earlier 2003 Tehran Agreement — illustrate how Iran used its nuclear program as leverage in negotiations with the West, seeking both sanctions relief and political recognition. However, especially with no nuclear agreement in place, Washington’s decision to initiate military action shattered the delicate balance that had previously dissuaded Iran from fully weaponizing its nuclear program.

The strike conveyed a clear message to Iranian leadership: the mere capacity for nuclear breakout is no longer sufficient to deter adversaries. Prior to the operation, international watchdogs maintained at least partial oversight of Iran’s nuclear activities; however, in the aftermath of Operation Midnight Hammer, Iran may likely move its program entirely underground. As such, the United States has pushed Tehran toward a posture of “all-fortressization”, a strategy of total militarization and nuclear deterrence akin to the path pursued by North Korea. This could mark the beginning of a hyper-militarized Iranian state, one that views a nuclear weapon not as a bargaining chip, but as a non-negotiable guarantor of sovereignty.

As a result of Washington's perceived unpredictability and unilateralism, some allies have begun to explore alternative security arrangements. In South Korea, public and political support for local nuclear weapons has grown with Foreign Minister Cho Tae-yul notably leaving open the possibility of pursuing such capabilities in response to North Korean threats. In Eastern Europe, Poland has expressed interest in acquiring nuclear weapons as part of its expanding defense posture in the wake of Russia’s 2022 invasion of Ukraine. Although Germany has not openly called for the development of its own nuclear arsenal, it has engaged in discussions with the United Kingdom and France regarding shared nuclear defense arrangements. This idea appears to be gaining traction, as evidenced by the recent Northwood Declaration, which reshapes the joint nuclear policy of France and the United Kingdom in Europe, and by the first bilateral treaty between the United Kingdom and Germany since World War II, which includes provisions for closer dialogue on nuclear posture. Meanwhile, in Japan, elements of the political leadership have increasingly voiced interest in reconsidering the country’s long-standing non-nuclear stance.

The U.S. action in Iran is likely to deepen these already existing fault lines. As allies seek to hedge against the perceived volatility of American foreign policy, a new wave of proliferation may emerge. This could involve new nuclear states or a broader geographic dispersion of existing nuclear weapons under shared or national control, both of which would pose significant challenges to the existing global non-proliferation regime. It is also important to recognize that the U.S. strike on Iran risks setting a dangerous precedent, namely, that nuclear-armed states may feel legitimized in using direct military force to prevent other states from acquiring or advancing nuclear capabilities.

The fact that the United States, traditionally seen as a global enforcer of non-proliferation norms, now claims the right to carry out such unilateral actions and transgress the very limits it once advocated could be seen as legitimizing similar behavior by other major powers, such as the PRC and Russia. Such actions could erode long-standing norms against preventive strikes on sovereign nuclear infrastructure, and in doing so, undermine the stability of the global non-proliferation regime. This precedent could be invoked by other major powers to justify aggressive action under the guise of strategic necessity. In this context, the fear that the U.S. strike against Iran lowers the threshold for such behavior is likely to accelerate global nuclear proliferation. States that perceive themselves as vulnerable to preventive military action may feel compelled to pursue nuclear weapons more urgently.