Looking to its legacy, the Obama administration may declare no first use of nuclear weapons. Some Asia specialists worried about North Korea argue against making such a pledge. That’s another reason it might be better for Washington to encourage its ally South Korea to turn to nuclear proliferation.

Washington has possessed nuclear weapons for more than seventy years. No one doubts that the United States would use nukes in its own defense. After all, America became the first nation to use the atomic bomb against Japan in World War Two.

However, since then Washington has extended a so-called “nuclear umbrella” over many of its allies that lack nuclear weapons. Exactly who is so protected and under what circumstances? No one really knows, especially with the Obama administration moving to narrow the circumstances for use of nuclear weapons.

Early in the Cold War, the United States threatened “massive retaliation” in Europe to offset Soviet conventional superiority. Once Moscow acquired an equivalent nuclear arsenal that approach lost appeal. Nevertheless, Washington still promised to use nuclear weapons in its NATO allies’ defense, though the precise circumstances under which the United States would act were not clear.

The United States also probably holds a nuclear umbrella over its Mideast allies. With perhaps two hundred of its own nukes, Israel doesn’t need American protection, though no election-minded U.S. politicians would admit as much. The United States could use nuclear weapons on behalf of Saudi Arabia and perhaps other friendly states, though that is far from clear. Certainly Washington is expected to prevent adversaries, such as Iran, from developing nukes. If Tehran moved ahead, some observers believe that Saudi Arabia, Egypt and Turkey would respond with their own programs.

Northeast Asia is the region where nuclear threats seem greatest. Japan and South Korea are thought to be snuggled beneath America’s nuclear umbrella, discouraging them both from acquiring their own weapons. Other possible claimants include Taiwan and Australia, though no one quite knows what Washington would do when. Presumably the guarantee to use nuclear weapons is in place against Russia, the People’s Republic of China and Democratic People’s Republic of Korea.

The “umbrella” obviously is defensive, that is, to protect American allies against the first use of nukes. However, Washington also could—and it appears would, if necessary, whatever that might mean—use nuclear weapons first to stop a conventional attack. While Moscow and Beijing might not be particularly friendly with America these days, they aren’t likely to attack the Republic of Korea or Japan. North Korea invading South Korea is more plausible.

Extended nuclear deterrence always has been risky for the United States. It means being willing to fight a nuclear war on behalf of others, that is, Americans would risk Washington, DC. and Los Angeles to, say, defend Berlin and Tokyo. At least bilateral deterrence among great powers tends to be reasonably stable, though credibility issues remain. Is Washington really willing to risk nuclear war over an issue of limited importance? The Chinese already have queried whether Americans believe saving Taipei is worth losing Los Angeles. It isn’t, or at least it shouldn’t be.

Dealing with North Korea is potentially more dangerous. While Kim Jong-un, like his father and grandfather, wants his virgins in this world rather than the next, his lack of sound judgment and stability are problematic. He might start a war inadvertently. Yet the DPRK eventually may gain the ability to strike the United States by developing long-range missiles as well as nuclear weapons. The North isn’t likely to attack first, but it still could lay waste to a major U.S. city, which would be bad indeed.

Yet advocates of extended deterrence are criticizing proposals for an American pledge of no first use of nuclear weapons. Writing for NK News, analyst Robert E. McCoy argued that the United States should not announce the conditions under which it would use nukes given Kim’s threats to use them: “It is imperative that Kim Jong-un is made to understand that he faces the destructive power of our entire weapons arsenal at all times when it comes to threatening the U.S. or its allies.”

Yet that is precisely the problem. It is one thing for Washington to use nuclear weapons, including preemptively, to protect America. It is quite different to do so for allies. Alliances are a means, not an end, that is, a mechanism to help defend the United States. A North Korean attack on South Korea would be awful, a humanitarian tragedy. But American security would not be directly threatened. Certainly there is no threat warranting the risk of nuclear retaliation on the United States.

Of course, those being defended have configured their security policy and force structure in response. The Brookings Institution’s Jonathan D. Pollack and Richard C. Bush note: “Non-nuclear states living in the shadow of nuclear-armed adversaries have long relied on U.S. security guarantees, specifically the declared commitment to employ nuclear weapons should our allies be subject to aggression with conventional forces.” But future policy should not be held captive to the past.

Pollack and Bush warn against putting allies’ security at risk. However, Washington’s chief responsibility should be America’s security. Backers of the status quo act like there is no alternative to leaving South Korea (and Japan, which faces a real, though less direct, threat from the DPRK) vulnerable to attack. However, Seoul is well able to deter and defeat the North. South Korea possesses around forty times the GDP and twice the population of North Korea, as well as a vast technological lead and an extensive international support network. Japan, which has long possessed the world’s second largest economy, also could do far more.

South Korea is capable of developing nuclear weapons. Indeed, a half century ago the current president’s father, President Park Chung-hee, dropped South Korea’s program under intense U.S. pressure. But interest in a South Korean bomb never entirely died, with polls showing public support for such an option today.

Opposition to nuclear weapons is stronger in Japan, but a South Korean weapon would put enormous pressure on Tokyo to conform. The United States should not press either nation to choose the nuclear option. However, Washington should indicate that it no longer plans to put its cities on the line for anything other than truly vital interests involving America, which are not at stake here.

Obviously, there are plenty of good reasons to oppose proliferation, even among friends. The more nuclear powers, the greater the potential for instability, proliferation and use. However, the alternative in this case is not stability, nonproliferation and nonuse. Rather, it is entangling Washington in the middle of other nations’ potential conflicts involving all of Asia’s threatening powers, China, Russia and North Korea. The result is to make America less secure.

Pollack and Bush write about “Northeast Asia’s inescapable realities.” However, precisely such realities suggest withdrawing the United States from that region’s nuclear imbroglio. Then America’s allies could engage in containment and deterrence, just as America did for them for so many years.

Doug Bandow is a Senior Fellow at the Cato Institute. A former Special Assistant to President Ronald Reagan, he is the author and editor of several books, including The Korean Conundrum: America’s Troubled Relations with North and South Korea (Palgrave/Macmillan, co-author).

Image: South Korean guard at the DMZ. Flickr/James Cridland