South Korea’s President Yoon Suk-yeol is visiting next week. The trip is a testament to how American liberals prefer working with Korean conservatives. President Joe Biden had far less affection for Yoon’s leftish predecessor, Moon Jae-in. Yoon is a foreign-policy hardliner, taking a tough line against North Korea, publicly criticizing China, and pushing for rapprochement with Japan. 

Yet the Biden-Yoon political love-fest highlights the fundamental bankruptcy of the alliance. Why is the ROK still dependent on the U.S. seven decades after the armistice concluding the Korean War? Why the blind inertia as America’s security guarantee threatens to become a transmission belt of nuclear war?

The alliance faces two serious challenges. First, South Korea no longer needs to delegate its defense to America. In 1953, an armistice halted the fighting, but no peace treaty ensued. In the early years China maintained a military presence in the North, while the Soviet Union remained hostile even after the death of Joseph Stalin. The South was economically wretched, politically unstable, and militarily vulnerable. America’s military presence was necessary for the Seoul government’s survival.

But that world is long gone. Today the ROK is a resilient democracy and possesses a more than 50-to-1 economic edge, enabling South Koreans to do whatever they believe necessary to protect themselves. In contrast, the DPRK is economically backwards, a victim of communist planning compounded by international sanctions. Years ago Kim Jong-un announced that his government’s “central task” was “to improve the people’s standard of living.” However, he has effectively declared defeat, and is today preparing them for greater hardship instead.

The North’s political future is uncertain, if not actively unstable. Although the Kim dynasty remains in control, its survival is by no means certain. Kim Jong-un once enjoyed American sports and culture, while welcoming South Korean K-pop artists to Pyongyang. Today he is waging a brutal campaign to prevent his people from learning how other Koreans live, even arresting children for dancing to the same music he once applauded.

North Korea’s conventional military capabilities remain limited, despite the DPRK’s routine splenetic threats. The North’s quantitative edge pales compared to the South’s sophisticated military, and Seoul could spend much more, if necessary, to maintain deterrence. 

Only nuclear weapons set the North apart, but that is no excuse for Washington’s heavy conventional presence. American troops are nuclear hostages, within easy reach of Pyongyang’s bombs, rather than security guarantors for the South. The U.S. could set the limit on its nuclear liability at responding to the DPRK’s use of nuclear weapons. Or Washington could entirely withdraw, leaving South Korea to initiate its own nuclear program. The downsides would be real, but an ROK deterrent still would be a better alternative for the U.S. as well as the South.

Other justifications have been offered for maintaining America’s security guarantee. One is to preserve Washington’s supposed influence over the South, but that appears to be more fantasy than fact. For instance, the U.S.-ROK free trade agreement, not the U.S. military presence, overcame Seoul’s protectionist instincts. Meanwhile, South Korean progressives long resisted hawkish security policies favored by the U.S. 

Another proposed objective is to contain the People’s Republic of China. But the ROK has good reason not to treat its oversize neighbor as a permanent enemy, since China, with its long memory, will always be there. A continued American presence is less definite, which is why Seoul probably wouldn’t back the U.S. against the PRC in a fight over Taiwan, thereby turning itself into a Chinese missile target. The South is likely to continue walking a fine political line between Beijing and Washington; even Yoon softened his tone after taking power.

It was also argued that America’s continued defense of the ROK would reduce non-proliferation concerns. So long as the ROK could rely on the U.S., the former would feel less need for its own nuclear weapons, which would require challenging Washington’s non-proliferation policies and risking loss of U.S. protection in retaliation. 

Yet non-proliferation should not be treated as a sacred totem. Nukes already have escaped Pandora’s box. Moreover, Washington is fully willing to overlook proliferation for political reasons—the U.S. has accepted, with varying degrees of enthusiasm, Israel, India, and Pakistan joining the nuclear club. The Biden administration should still generally discourage the spread of nuclear weapons, but America’s interest in doing so is less important than avoiding U.S. involvement in war, especially a serious conventional fight that could go nuclear.

There also is much talk about expanding the alliance, giving it a global focus. That makes little sense if the North’s threats are thought to be too great for the South to confront. Then Seoul should concentrate on protecting its vital interests rather than promoting Washington’s global priorities. If there is no such danger, then there is no need for an American defense commitment, or to link bilateral security, political, and economic cooperation to one. The present “Mutual” Defense Treaty was created to protect South Korea. Yet even extensive cooperation between Seoul and Washington in other areas does not depend on America defending the South.

The ROK’s diminishing need for U.S. support is only half of the equation. The second factor is the increasing danger posed by America’s defense guarantee as the North expands its nuclear program. Despite the economic hardship afflicting the DPRK, Kim’s military has been pursuing a long list of innovations and improvements. Although the DPRK cannot compete on the conventional battlefield, Pyongyang is becoming a potentially significant nuclear power.

For the first half century or so of the alliance, Washington’s policy of “extended deterrence,” which included the promise to use nuclear weapons to defend the South if necessary, seemed relatively cheap. Although conventional combat in any conflict would be fierce, as in the Korean War, the American homeland would be safe, well beyond Pyongyang’s reach. That relative immunity is disappearing. The DPRK has been moving ahead militarily in many areas, including developing missiles and nuclear weapons. 

Indeed, the North has been dramatically expanding its repertoire, experimenting with tactical nuclear weapons, submarine-launched ballistic missiles (SLBMs), and cruise missiles. The DPRK also is working on multiple independent re-entry vehicles, or MIRVs. Most ominous for America, North Korea is building intercontinental ballistic missiles (ICBMs). Pyongyang began with liquid fuel models, but recently tested one using solid fuel. The North Korean news service declared that “the development of the new-type ICBM Hwasongpho-18 will extensively reform the strategic deterrence components of the DPRK, radically promote the effectiveness of its nuclear counterattack posture and bring about a change in the practicality of its offensive military strategy.” These developments reflect a prodigious missile testing program, with nearly 100 launches last year and more than twenty so far this year.

Unfortunately, at present production rates, Pyongyang is likely to have more than enough nukes to place atop its many missiles. Today the regime likely possesses enough fissile material for perhaps forty-five to fifty-five weapons, although the number could be higher. The Rand Corporation and Asan Institute warn that the North could amass as many as 240 nuclear weapons over the next few years, which would firmly place it among the secondary nuclear powers. Even if Pyongyang ends up with fewer nukes, the DPRK will possess the means to devastate the American homeland. That will require the U.S. to reconsider its promise to get involved in another war on the Korean peninsula.

Most likely, Kim Jong-un is seeking leverage rather than conflict: He wants to own a sufficient number of nuclear weapons to force the lifting of some if not all sanctions while remaining a nuclear power. The ability to incinerate American cities would make real the question of whether the U.S. is ready to sacrifice Los Angeles for Seoul. In just a few years, America may be risking Chicago, Houston, New York City, and Washington, D.C. as well.

Imagine the outbreak of conflict on the peninsula, with the U.S. sending mass reinforcements. Then, as in 1950, the allies defeat the North Korean invasion forces and drive the latter north, but China, in contrast to last time, stays out of the conflict. Victory, and the destruction of Kim’s regime, appear at hand, at which point the North’s latest god-king announces that unless Washington pulls back he plans to strike American cities. With the Kim dynasty at risk—and regime members facing ouster, arrest or exile, imprisonment, and perhaps even death—the threat is credible. What should the American president do? 

Today Washington’s plan is to only become more deeply entangled in the Korean imbroglio. Amid the North’s ongoing military build-up, National Security Council spokesman John Kirby said: “So we will continue to make sure that we have the appropriate military capabilities and the appropriate readiness to use those capabilities if need be, to protect our national security interests and those of our allies.” 

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Yet defending allies is not the same as defending the U.S. The former should be but a means to the latter end. The president’s responsibility is to the American people, not South Koreans. American policy should reflect that, in theory and practice. Fear that Washington might adopt such a policy is why extended deterrence is becoming a controversial issue in Seoul, with support growing for an independent nuclear deterrent. 

And that is why the policy should be equally controversial in the U.S., leading to a serious rethinking. Ending “extended deterrence” need not leave the ROK helpless in the face of a North Korean nuclear attack. Rather, Seoul could choose to match its northern neighbor. This obviously would not be ideal—even friendly proliferation would create practical difficulties. However, the strategy is popular in the South and could help restrain China as well as the DPRK. Ultimately, American interests are best advanced by expecting allies, such as the ROK, to take over their own defense when possible. Then Washington and Seoul could refashion a broader cooperative agreement between equals covering military and other issues.

Seven decades ago America might have been the essential nation for South Korea. Vain American policymakers still enjoy imagining themselves to be the ROK’s essential protectors. However, the necessity for American involvement in the Korean Peninsula has disappeared. Long ago South Korea should have graduated from the U.S. defense dole. At the upcoming summit the two countries should discuss how to make it so, thereby enabling America to shed, rather than share, defense responsibilities for the peninsula.