The Future of Nuclear Non-Proliferation in East Asia Depends on Iran

T he world is currently mired in nuclear-induced instability in the Middle East. Yet an even greater nuclear shock looms in the Pacific if the U.S. is not careful. South Korea and Japan have both expressed concern that the Iran war has pulled U.S. military forces away from their defense. Questions abound in both countries about the credibility of Washington’s security commitment. Unless the U.S. adjusts its diplomatic and military posture in the war’s aftermath, the spread of nuclear weapons in East Asia is a real possibility.

To be sure, the ongoing military campaign in Iran could strengthen the barrier to nuclear proliferation. America’s last four presidents all committed to taking action should the ayatollahs stand poised to cross the nuclear finish line. After years of uncertainty, Donald Trump has upheld that commitment by degrading Iran’s nuclear infrastructure and missile arsenal — and for good reason.

An Iran armed with nuclear-tipped missiles would not only constitute a severe threat to the U.S. and its allies, but it would also pose an existential threat to the global nonproliferation regime. Saudi Arabia might spring for nuclear weapons should Iran acquire its own. And this in turn might lead U.S. allies in East Asia to conclude that America’s commitments — whether to nonproliferation or to allied security — count for little. After all, hasn’t every U.S. president since George W. Bush pledged to thwart Iran’s nuclear ambitions?

Credibility matters in international politics. Once it is lost, it is not easy to recover. This fact of life is therefore important for President Trump to keep in mind as concerns grow in East Asia about America’s treaty obligations.

Seoul recently expressed its opposition to the Pentagon shifting missile interceptors from South Korea to the Persian Gulf to fend off Iranian attacks. This move comes at an inopportune moment from Seoul’s perspective, as it coincides with North Korea’s live-fire exercise of nuclear-capable artillery rockets. It also follows the publication of Mr. Trump’s National Defense Strategy, which suggests that Seoul should assume “primary responsibility” of deterring its nuclear-armed neighbor to the north. Worse still, the National Defense Strategy inauspiciously omits the standard reference to America shielding South Korea under its nuclear umbrella.

Seoul was already questioning the credibility of U.S. security assurances prior to the Iran war. There is little doubt then that it will be watching closely to see how the U.S. postures its military forces in East Asia after the war ends.

How exactly the U.S. adjusts its stance will likely impact the ongoing debate in Seoul over whether it should continue relying on the U.S. nuclear deterrent. South Koreans clearly desire stronger security guarantees. What remains unclear is whether those guarantees come from Washington revamping its regional nuclear posture or from South Korea building its own nuclear weapons.

The same goes for Japan. Tokyo recently looked on as a U.S. Marine expeditionary unit departed Okinawa for the Middle East. This move follows Trump’s failure to back up Japan last December as it faced severe political, economic, and military pressure from China. Prime Minister Sanae Takaichi had elicited Beijing’s ire by complying with the Pentagon’s demand that she publicly acknowledge that a Chinese attack on Taiwan could trigger a Japanese military response.

Tokyo stepped up to the plate knowing full well the consequences — only for Trump to leave Japan high and dry as Chinese fighter jets aggressively probed its air defense. Little wonder then that Takaichi initially refused to reaffirm Japan’s nonnuclear principles in the immediate aftermath of China’s pressure campaign. One Japanese official even went so far as to suggest that his country should acquire nuclear weapons.

There is plenty to balk at regarding the prosecution of the ongoing war in Iran. Trump appears to have shifting war aims, and terminating a conflict is difficult when you do not know where you are headed. Knowing your final destination is especially important when U.S. munitions stockpiles are depleted and insufficient to uphold alliance commitments in East Asia.

But if Trump manages to land a devastating blow on Iran’s nuclear infrastructure and missile arsenal, and if he follows that up with stronger security ties to East Asia, then he will have bolstered the nonproliferation regime in a serious way. Let’s hope Trump follows through.