With North Korea shelling a South Korean island, and Seoul responding in kind, fears of a second Korean War are wafting through Washington. Thankfully, even Pyongyang doesn’t want to revive that conflict, but the possibility of mistake and accident remain.

Naturally, the United States reiterated its usual security guarantees. The White House said America was “firmly committed” to the South’s defense. But why is Washington mixed up in potential hostilities on the Korean Peninsula?

The U.S. commitment grew out of World War II. Washington divided occupation duties on the peninsula, a colony of defeated Japan, with the Soviet Union. Two separate countries emerged, followed by a three-year conflict, in which America intervened. In 1953 the warring sides agreed to an armistice. The United States gave South Korea a defense treaty and military garrison to keep the peace.

Since then the world has changed. The Republic of Korea has rushed past its northern antagonist economically. With the thirteenth-largest economy in the world, the ROK now has about forty times the GDP of the Democratic People’s Republic of Korea. South Korea also has twice the DPRK’s population, as well as a vast technological edge.

Moreover, Seoul has detached North Korea’s traditional allies. The Soviet Union went AWOL under Mikhail Gorbachev. Although Vladimir Putin’s Moscow has somewhat repaired its relationship with Pyongyang, Russia still has a far more important economic relationship with the ROK. So does China, which trades fifty times as much with the South as with the North.

Only in military strength does the DPRK retain a numerical edge over Seoul. North Korea has 1.1 million men under arms, an impressive number, but individual conscripts tend to be malnourished and of uncertain quality. Their weapons are antiquated. A prime fighting force the North Korean military is not. The South only has about seven hundred thousand men under arms, but they are better trained and deploy better weapons.

In any case, Seoul has the resources to provide whatever it believes necessary for its own defense. There is no special gravitational field on the peninsula that keeps the ROK military numerically inferior. South Korea simply prefers to spend its money on economic development.

It was one thing for the United States to subsidize the South’s defense when that nation was vulnerable to an attack by the DPRK backed by China and the Soviet Union. That’s no longer the case. America’s military commitment also didn’t seem to matter much when no one imagined another war was really possible. When the North’s “Dear Leader” Kim Jong Il was holding summits with South Korea’s presidents, conflict seemed far away.

But last March the DPRK apparently sank a South Korean warship. Seoul did little, other than demand an apology—a demand which the government of President Lee Myung-bak recently retracted. Now the North has staged another violent incident. Even though Pyongyang almost certainly does not want war, its provocative behavior risks triggering one, a conflict in which the U.S. would immediately become involved.

In fact, there have been proposals for retaliation against the North backed by Washington. Such a step could start a war directly.

There’s no justification for keeping the United States in between the two Koreas. It is long past time for Seoul to develop whatever size military it believes to be necessary and whatever policy towards the North it believes to be appropriate—and to accept the consequences accordingly. The ROK is strong enough to do what important countries traditionally have done throughout history, defend itself.

Washington’s one area of genuine interest, nonproliferation, is not advanced by a troop presence in the South. In fact, those are the only Americans within the North’s reach. They are, in effect, nuclear hostages if Pyongyang develops nuclear weapons and delivery systems.

The latest intra-Korean skirmish should serve as that proverbial fire bell in the night. Alliances can deter. They also can entangle. In the case of South Korea the security relationship risks drawing the United States into war with no countervailing benefits for Americans. After all, the ROK no longer is central to a larger international struggle, as it was during the Cold War. And the South is capable of deterring the DPRK and winning any conflict that might erupt.

Pyongyang’s ongoing antics left the Obama administration with nothing useful to say. After the revelation of the uranium-enrichment facility, State Department spokesman P. J. Crowley announced: “We will not be drawn into rewarding North Korea for bad behavior.”

Then came some really bad behavior. White House press secretary Robert Gibbs declared: “The United States strongly condemns this attack and calls on North Korea to halt its belligerent action and to fully abide by the terms of the armistice agreement.” No doubt, the DPRK will be quick to comply.

There are still some who hope that negotiations can resolve the confrontation on the peninsula. Indeed, the North’s provocations most likely are intended to stoke up tensions in hopes of winning allied concessions through new talks. Yang Moo-jin, a professor at Seoul’s University of North Korean Studies, argued: “The North reacts with sea clashes whenever it feels slighted or threatened.” However, Washington and Seoul have played this game before. The outcome is never peace, but rather a new round of provocations.

Moreover, there could be more at stake. “Dear Leader” Kim Jong Il might be attempting to generate a crisis atmosphere domestically to enhance the prospects of his youngest son succeeding him. Or the military might be flexing its muscles, with the politicians fearful of limiting its activities with a power struggle impending.

As is its wont, Beijing assessed no blame, blandly expressing “concern over the situation” and hope that “the relevant parties will do more to contribute to peace and security on the peninsula.” However, there is no reason to resume the six-party talks or any other forum unless the People’s Republic of China commits to doing more than offering platitudes from the sidelines. The PRC keeps the Kim regime afloat with bountiful shipments of energy and food. That should change.

If Beijing wants to take on a leadership position in Northeast Asia, it should start with North Korea. That means joining with the U.S., South Korea, and Japan in developing a benefit package which would reward the North for denuclearization, backed by the threat of real sanctions, meaning a cut-off of all subsidies, investment, and trade.

In return, the allies would promise not to take geopolitical advantage if the Kim dynasty collapsed. The democratic powers would give the PRC a free hand militarily if there was disorder along China’s border, provide aid if regime collapse led to mass refugee flows across the Yalu River, and withdraw all U.S. troops from the peninsula if reunification became a reality.

But if the Chinese government continued to subsidize North Korea—the former actually has increased economic investment in recent months—then Beijing would bear the consequences of any collapse and conflict. The current situation is highly unstable and Washington should state its intention to turn over policy to Seoul, which is most vitally affected by the DPRK’s behavior. Moreover, Washington should indicate that it would not be inclined to remain involved and block Seoul and Tokyo from responding in kind if the North continued to develop nuclear weapons. North Korea is a potential nightmare for China no less than for the United States.

It’s déjà vu all over again, opined Yogi Berra, and so it is in Korea. The most important lesson for Washington is that it’s time for the United States disengage militarily, leaving South Korea’s defense up to South Korea. James Carafano of the Heritage Foundation says the North is a “clear and present danger.” It is—to the ROK. But Americans are at risk only if the U.S. government puts them in harm’s way by guaranteeing the South’s security and garrisoning the peninsula.

Doing so was necessary in 1953. But not today.

The Korean peninsula remains one of the most dangerous international tinderboxes. The South Koreans should take over as geopolitical firemen in their own neighborhood. Washington should refocus its attention elsewhere.