South Korea’s President Moon Jae-in is trying to find the thin line between conciliating the North and satisfying America. Neither is easy; doing both is well-nigh impossible. But the key to success lies in following up on a pledge made by President Moon late last year.

In speaking to the Republic of Korea’s (ROK) National Assembly, he advocated that Seoul “retain overwhelming military superiority” against the Democratic People’s Republic of Korea, in order to respond “to provocations by North Korea.”

Toward that end the Seoul government is increasing the defense budget 6.9 percent this year, the most in a decade. The purpose, said Moon, was to “make our armed forces stronger and to equip them with self-reliant national defense capabilities.”

Hopefully Moon is serious. If so, he could end up successfully managing relations with both the U.S. and DPRK.

America’s current involvement in the Korean Peninsula began at the conclusion of World War II, when the victorious powers were left to decide what to do with the defeated Japanese empire’s Korean colony. The U.S. and Soviet Union split the peninsula, leading to two occupation zones and then independent countries.

In 1950 North Korea’s Kim Il-sung sought to conquer the South, with the support of Moscow and Beijing. He almost won, but ultimately was routed by U.S. forces, which in turn were forced to retreat by Chinese “volunteers.” In 1953, the fighting ended in an armistice and Washington offered a security guarantee to the ROK. Absent American support the South would have been vulnerable to another assault.

However, that world long ago disappeared. In the 1960s South Korea took off economically. Democracy emerged after another quarter century. The ROK’s development continued in succeeding years. In contrast, the DPRK stagnated, a totalitarian backwater that was little more than an army with a state, as Prussia once was described.

Somewhere along the way Seoul could have taken over its own defense. Today South Korea enjoys about 45 times the GDP and twice the population of the North. While economics alone is not destiny, the ROK has the obvious wherewithal to build a force of whatever size and however equipped necessary to deter or defeat the DPRK. In recent years, America support has operated as not only a subsidy for a wealthy friend but also a deterrent to it doing more, even when facing a genuine existential threat. The main reason South Korea has not attained “military superiority” and “self-reliant defense capabilities,” in President Moon’s words, is because of the attraction of America’s defense dole.

Therefore, to achieve his desire to truly put South Korea’s defense in South Koreans’ hands, President Moon will have to sacrifice his nation’s dependence on America’s taxpayers. Which means his countrymen must be willing to pay the potentially high price. Counting military units deployed outside the peninsula available for a possible Korean contingency, Americans probably spend more than South Koreans on the latter’s security.

Seoul appears poised to begin building a more effective missile deterrent. Last fall the Trump administration removed payload limits on South Korean missiles, a bizarre, antiquated limitation that made no sense at a time when the North was developing ICBMs. Years ago, when the ROK was viewed as little more than a puppet state, Washington worried about spurring a regional arms race. But with the DPRK and China racing ahead and Japan at least beginning to walk the race, it makes no sense to limit the South.

Even more fundamental is the nuclear question, however. President Park Chung-hee, uncertain of President Richard Nixon’s continuing commitment to the ROK’s defense, began a nuclear program that he ended only under enormous American pressure. South Korean politicians have begun to raise the issue, and two-thirds of South Koreans indicate their support for their own nuclear deterrent.

So far President Moon says no. In his speech to the National Assembly he cited the 1992 Joint Declaration with North Korea which “makes it impossible to accept or acknowledge North Korea as a nuclear power.” So the ROK also will not develop nukes, he explained. But Pyongyang long ago tossed that pact in the trash. Instead he would have his nation rely upon Washington. The opposition is even worse, calling for redeployment of U.S. tactical nuclear weapons to the peninsula.

However, once the North possesses the means to strike the American homeland, which seems inevitable, then an American president would have to be willing to risk Los Angeles, Seattle, Honolulu, and perhaps many other cities to protect Seoul. The ROK’s ties with the U.S. are many, but they are not worth that risk. And no matter what the U.S. president might promise to do, South Korea could never be certain that he would do so.

Objections even to a democratic ally of the U.S. possessing nukes are obvious. However, nonproliferation is having effectives similar to domestic gun control: Only the bad guys have guns, in this case China, Russia, and North Korea. Washington is supposed to guarantee the nuclear security of Japan and South Korea, as well as — maybe — Australia, Taiwan, the Philippines, and who knows else? At potentially great cost. Such a policy makes America less rather than more secure.

Moreover, for the ROK the basic question is who decides its fate. President Moon insisted: “We must decide the fate of our own nation. We will not repeat the unfortunate history of having our fate decided regardless of our wishes, such as the colonial rule and the division” of the peninsula.

But that can’t happen so long as the Seoul government allows the U.S. to decide Korea policy. The ROK can say yes to its future only if it says no to America. Could President Moon be the first South Korean president willing to do so?