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Will South Korea Build Nuclear Weapons?

South Korean F-35 Joint Strike Fighter. Image Credit: Creative Commons.
South Korean F-35 Joint Strike Fighter. Image Credit: Creative Commons.

South Korea’s President Mentions the Possible Nuclearization of His Country – South Korea’s President Yoon Suk Yeol suggested in a press conference last week that South Korea might develop its own nuclear weapon. There has been a rolling debate in South Korea for about a year on its potential nuclearization.

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But that has been mostly limited to extra-governmental voices in think-tanks and academia.

So it is genuinely surprising that this has already reached the presidential office.

Indeed, it speaks to just how threatening North Korea’s nuclear weapons are perceived in South Korea – and how unhelpful China has been in restraining Pyongyang – that no less than its president is now discussing this.

The Argument for South Korean Nuclear Weapons

I have written about this elsewhere, but the brief version of the South Korean argument for nuclear weapons is that US extended deterrence over South Korea is less credible since North Korea developed the ability in 2017 to hit the continental United States with a nuclear weapon. Indeed, striking the US homeland is almost certainly why the North Koreans built an intercontinental ballistic missile (ICBM).

North Korean supreme leader Kim Jong Un and his cronies are not crazy or insane. They are highly unlikely to launch a first strike on the US or its allies. That would entrain massive US retaliation, eliminating the Kim regime and devasting the country. Instead, the purpose of North Korea’s nuclear ICBMs is to push the Americans and South Koreans apart. Ukraine is an example of how North Korea might leverage strategic nuclear threats to block or reduce American assistance to South Korea in time of need.

Ukraine is not a US ally, of course. South Korea is. But the analogy roughly works. Russian President Vladimir Putin has, since the start of his war, made oblique nuclear threats against the West to limit its assistance to Ukraine. It is irrelevant if Putin was bluffing or not (he probably was). What mattered was the uncertainty he stirred up in Western capitals.

We know that Russian nuclear threats deterred the West from setting up a no-fly zone over Ukraine in March, when Kiev was begging for that. (And NATO still has not done that.) We also know that NATO member states have been unwilling to transfer too many weapons and their most modern weapons to Ukraine for fear of crossing a nuclear red line with Putin. Finally, Russia’s nuclear status has provoked great debate over just how far the Ukrainians should push for final victory. Specifically, if Kiev tries to take Crimea – which Putin snatched back in 2014 – would that be a bridge too far?

In short, while NATO has not abandoned Ukraine for fear of Russian nuclear weapons, its commitment, transfers, and zeal have been blunted by them. The South Korean fear is similar: in a spiraling crisis with North Korea, would its nuclear ICBMs compel the US to ‘slow-roll’ assistance for fear of crossing some retaliation threshold with North Korea?

The answer is almost certainly yes. It is inconceivable now, in a nuclearized environment, that the US alliance commitment to South Korea is as automatic as it was in a conventional environment. Any US president will flinch at a course of action which might realistically incur a nuclear strike on US cities.

This new reality, since North Korea’s successful 2017 ICBM test, is only just sinking in. For a few years, it looked like former US President Donald Trump and former South President Moon Jae In might strike a deal with North Korea. That was always pretty far-fetched, but once it definitely fell apart by 2020, a South Korean nuclear debate was likely inevitable.

America’s Response

The debate on nuclearization in South Korea itself is culminating. South Korea public opinion is supportive. Nongovernmental opinion is tilting toward it. The country’s main conservative party has said South Korea should withdraw from the Non-Proliferation Treaty if North Korea tests another, seventh, nuclear weapon. And now the South Korean president has broached the issue too.

The big hurdle then is the Americans. The US is South Korea’s only treaty ally and its core foreign relationship. Without American defense guarantees, South Korea’s defense spending would double or triple. So South Korean governments have traditionally given American preferences wide berth.

And indeed, the American response was to play down Yoon’s comments.

But I doubt this position is sustainable over the long, or even medium, term. The North Korean nuclear threat is not going away. There is no denuclearization deal to be had with them – Trump and Moon’s failure proved that – and China will not help. In fact, the North Korean nuclear and missile threat will only worsen as the regime tests more and more, and they certainly are not going to stop. The more North Korea can threaten US cities with massive destruction, the less credible US alliance guarantees will be.

Luckily, this problem is not new. America’s European allies faced it during the Cold War because the USSR could strike the US homeland, and a variety of responses, including nuclear sharing and indigenous nuclearization, were tried with reasonable success. The US has also adapted to Israeli, Indian, and Pakistani nuclearization without a massive crisis.

So South Korean nuclearization need not lead to an alliance rupture unless the US insists on it.

Expert Biography: Dr. Robert E. Kelly ( is a professor in the Department of Political Science at Pusan National University and 19FortyFive Contributing Editor.

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Dr. Robert E. Kelly (@Robert_E_Kelly; website) is a professor of international relations in the Department of Political Science at Pusan National University. Dr. Kelly is now a 1945 Contributing Editor as well.