To read the seismic signal sent from an abandoned coal mine in the mountains of North Korea's coast, you must first recognize that it represents four major failures, two grave dangers, and one big opportunity.

The apparent explosion of a nuclear device, coming after two decades of trying to stop North Korea from achieving this goal, is a manifest failure of policy on four fronts -- a failure of U.S. nuclear non-proliferation policy, a failure of international diplomacy, a failure of Chinese leadership and a failure of South Korea's strategy of engaging the North.

Having failed so completely, the world now faces two grave dangers. The first is the very real threat of war on the Korean Peninsula, triggered by a series of escalatory actions in the wake of the bomb test. The second is the danger that North Korea will proliferate its nuclear technology, materials or know-how to others -- not the least to another nuclear hopeful, Iran.

But there remains a lone and tenuous opportunity. Having removed all ambiguity about its nuclear ambitions, North Korea may finally have created a common sense of threat that will galvanize the kind of concerted international action that so far has been absent.

THE FOUR FAILURES

Non-proliferation failure

The United States has spent two decades trying to stop North Korea from going nuclear, a turbulent period of crisis and negotiation that even went to the brink of war. At least three administrations confronted this problem and none, certainly not the Bush administration, can escape blame.

North Korea agreed to sign the Nuclear Non-Proliferation Treaty (NPT) in 1985, but it stalled before signing an agreement with the International Atomic Energy Agency (IAEA) in 1992 to place its nuclear facilities under international safeguards and inspections. During that time the North Koreans reprocessed some spent fuel from their reactor into plutonium - an amount that American intelligence believes was enough for building one or two warheads.

North Korea's resistance to full inspections, while it kept pulling spent fuel rods out of its reactor, provoked a crisis in 1994 and led the Clinton administration to ready military forces to strike the North's nuclear facilities. In a last-minute deal, North Korea froze its reactor and reprocessing facilities, effectively halting plutonium production under IAEA supervision. In exchange, the United States, Japan, South Korea and others agreed to construct two light-water reactors for North Korea and to supply fuel oil until the reactors came online.

The deal was troubled from the start. Neither party was satisfied with the compromise or the way it was to be implemented. By the late 1990s, the North had begun a secret effort to acquire uranium-enrichment technology from Pakistan and, in 1998, tested a long-range ballistic missile. Despite this, the plutonium freeze remained in place. But it did not survive the Bush administration.

The Bush administration came into office challenging the value of the agreement and froze contacts with the North. After receiving intelligence showing moves to build enrichment facilities, it confronted North Korean officials at an acrimonious meeting in Pyongyang in October 2002.

The United States halted fuel shipments a month later, and, in early 2003, the North Koreans expelled IAEA inspectors and withdrew from the Non-Proliferation Treaty. They proceeded to reprocess the fuel rods they had stored for a decade, producing enough plutonium, intelligence estimates say, for four to six nuclear warheads. In February 2005, the North Koreans announced they had manufactured nuclear weapons. Last week, they apparently made good on that declaration.

Blame aside, North Korea's emergence as the world's ninth nuclear power may be the most serious failure in non-proliferation history. Unlike India and Pakistan, which remained outside the system of international treaties, North Korea acted in defiance of those controls. Who might be next?

Diplomatic failure

Unlike Iraq, the attempt to stop North Korea's nuclear program has relied on the tools of diplomacy, accompanied by economic incentives and coercive sanctions.

But serious questions have been raised from the start about the sincerity and methods of the diplomatic efforts, particularly on the part of the United States and North Korea. The Bush administration has insisted -- and the president continues to make this argument -- that direct talks with North Korea do not work. Pyongyang has tried to frame everything as an issue with Washington, undermining talks that involved others, including South Korea.

Bush's stance lends credibility to those who charge the administration seeks "regime change," not a compromise that it believes will lend legitimacy to Kim Jong Il. The North Koreans now appear to have used the talks to buy time and build bombs.

Diplomacy has, at American insistence, consisted of six-party talks, held under Chinese auspices and including both Koreas, Japan and Russia. In truth, little real negotiating went on at these gatherings, at least until the last full round of talks in September 2005. In contrast to the thousands of hours of negotiations between Americans and North Koreans that led to the 1994 deal, there have been only tens of hours of actual give and take.

It is intriguing that the September agreement on a statement of principles for denuclearization came only after the State Department's chief negotiator was finally allowed to talk to his North Korean counterpart at length. Even then, their agreement evaporated almost immediately as they dueled publicly over the deal's meaning. American financial sanctions against North Korean currency counterfeiting further clouded the atmosphere, and direct contacts ground to a halt.

China's failure

The North Korean nuclear crisis is also a failure of China's bid for regional, if not global leadership. North Korea is an ally of China, a relationship that goes back more than half a century to the Korean War, when Chinese "volunteers" poured across the border to prevent an American victory. Their relationship has become more difficult since China embarked on market reforms while North Korea clung to its peculiar brand of Stalinism.

China has been torn between its loyalty to Pyongyang, its desire to maintain a stable balance of power in the region and its fear that the North's nuclear ambitions could provoke conflict on its borders. By becoming host for the six-party talks, Beijing stepped into an unusual leadership role.

The Bush administration was eager to move the burden of the North Korean problem onto the Chinese. Some administration hard-liners argued that China had the power to trigger the collapse of Kim Jung Il's regime by cutting off energy and food supplies.

Time and again, Beijing dragged the North Koreans back to the negotiating table, while also pushing Washington to engage Pyongyang in the talks. But Chinese irritation over American inflexibility has now been trumped by North Korea's defiance. Chinese policy-makers now wonder how they can punish the North without creating chaos, or war.

Failure of engagement

The final failure lies on the doorstep of South Korea's 10-year-long policy of engagement. The "sunshine policy" asserted that the North could be induced to give up its nuclear option by opening up the isolated communist state and promoting the forces of Chinese-style reform.

After a historic summit meeting in 2000, South Korean aid and trade, even tourists, flowed into the North. South Koreans lost their fear of a former foe, seeing it more as an impoverished lost brother than a mortal threat. Tensions with their American allies rose because of a gap in the North's perceived threat. The United States wondered why its troops should continue to defend South Korea.

Now South Koreans must confront the possibility that the North may have used engagement only to buy time.

THE TWO DANGERS

Threat of war

With eyes on Iraq and the Middle East, the Korean Peninsula has been far from the center of American attention. American forces based in South Korea and Japan have been dispatched to Iraq.

Yet the demilitarized zone that separates the two Koreas remains the most militarized frontier on the planet, with hundreds of thousands of well-armed soldiers poised against each other. Clashes along that frontier used to be commonplace and there are signs of a renewal of tensions. The danger of unintended escalation cannot be dismissed.

What might happen if a U.S. naval vessel, moving to inspect a North Korean freighter - as the U.N. resolution may authorize - is fired on or even captured, as the USS Pueblo was in 1968? It is a frightening scenario already worrying some at the Pentagon and the State Department.

Risk of proliferation

More than anything else, American policy-makers fear that North Korea, emboldened by its nuclear success and perhaps desperate for funds amid economic sanctions, might sell its nuclear expertise to Iran and others, including terrorist groups.

For Pyongyang, an alliance with Iran is a logical response to American and global pressure. The North Koreans have sold ballistic missiles to Tehran since the 1980s and rumors of nuclear cooperation persist.

An American effort to interdict the movement of ships and planes to Iran -- with possible U.N. backing - is probable. But the most likely transit is across the long and loosely controlled land border with China. The amount of plutonium needed to make a warhead is the size of a grapefruit and hard to detect - creating yet another nightmare scenario.

THE OPPORTUNITY

In this otherwise bleak landscape, there is an opportunity. For the first time, there is a chance of a consensus among the key players -- China, Japan, South Korea, Russia and the United States. The passage of a U.N. resolution is a small step in that direction. But the real test will come next, as the nations must cooperate to put pressure on North Korea, while coolly navigating the perils of war and making sure to leave open a diplomatic exit.

There is a slim chance of such concerted action, and a limited window for achieving it. Not everyone sees the dangers the same way. Signs of rethinking errors of the past are no more evident in Beijing and Seoul than they are in Washington or Tokyo. Ultimately, however, if they are to seize this moment of opportunity, all parties must face up to the fact that the policies of the past have failed.

North Korea's announcement this week of plans to test a nuclear weapon is hardly surprising. The six-party talks to negotiate an end to its nuclear program are dead, and the North faces escalating financial and economic sanctions by the United States and its allies.

Experts have long debated the real motivations of the North in developing nuclear weapons. Some contend that the nuclear program, even the latest pronouncement, is simply a bargaining chip to gain security guarantees and economic aid. Others see a long determination to become a nuclear state.

The North Korean leaders may have begun the nuclear program as leverage. But the U.S. invasion of Iraq seems to have hardened their conviction that the only way to protect their nation and their regime is to join the nuclear club. The North Koreans want to become a Pakistan rather than an Iraq.

Still, officials in Pyongyang hesitated to cross the provocative line of visibly demonstrating their capability. Pressure is being mounted to get them to back down from their pledge. But for a variety of reasons, they apparently believe the timing for a test is now optimal.

First of all, they hope to blame the Bush administration for their decision. In the statement issued this week, the North Korean government argued that alleged American war plans justify a nuclear test, a position that reflects the views of the North Korean military.

Second, the North anticipates the test will be successful. Although a plutonium weapon is more complicated than a uranium bomb, it is quite likely that the North now has sufficient confidence in a Nagasaki-style primitive bomb. This success would be an object of pride for an otherwise failing state, and bolster its claim to the status of a world-class military power.

Third, the North Koreans see their potential enemies tied down and unable to respond effectively. The Bush administration is locked into a disastrous war in Iraq, and about to be weakened even more if the Republicans lose the upcoming midterm elections. In South Korea, the government of President Roh Moo Hyun is already a lame duck and politically paralyzed.

Fourth, Pyongyang may bet that China and South Korea, the two principal sources of trade and economic aid, would not join the United States and Japan in any real sanctions against the North. The July missile tests by North Korea provoked international uproar and led to a U.N. resolution. But the real impact has been minimal.

Finally, the North may calculate that testing will facilitate Japan's efforts to become a "normal'' nation with a broader military role in the region. That prospect could increase tensions in Northeast Asia, especially between Japan and China, and that, the North may believe, is not necessarily bad for it.

The United States, South Korea and China must act together to show that these calculations are misguided and that the North will pay a painful price if it goes ahead. Certainly this severely tests the troubled American alliance with South Korea and the emergent partnership with China. But Pyongyang's miscalculations also offer an opportunity to repair the strained alliance and create a new structure of security cooperation in Northeast Asia.

It is no secret that Seoul and Washington have been at odds over how to deal with North Korea. But the test announcement has already accelerated a shift in South Korean opinion. Rather than holding the United States responsible for the current impasse, most Koreans now see North Korea as the instigator of crisis.

South Korean officials understand that without reinforcing the alliance now, no policy toward the North can be effective. The United States and South Korea should urgently agree on common action plans -- including a shutdown of investment and economic assistance from the South to the North -- and make those consequences clear to Pyongyang.

The planned visits of newly installed Japanese Prime Minister Shinzo Abe to Beijing and Seoul next week offer a similar opening to turn threat into opportunity. Abe intends to repair tattered ties to those Asian neighbors. Now the three Northeast Asian powers can demonstrate that a nuclear test will not lead to increased tensions but to the complete isolation of the North.

The danger of escalating actions that could lead, again, to war on the Korean peninsula is grave. The North Koreans should be assured that the door to a diplomatic solution remains open to them. But they must also understand that by profoundly misreading this moment, the North Korean leadership now stands completely alone in Northeast Asia.

Reprinted by permission.

The U.S. visit this week by South Korean President Roh Moo Hyun offers yet another opportunity to bemoan the crisis of confidence in our alliance. Anti-American views, particularly among the young, remain widespread in South Korea. On an official level, there are strains over the role of U.S. troops based in Korea and a stark divergence in approaches toward North Korea.

This portrait of a troubled alliance is often contrasted with a supposed golden age in U.S.-Korean relations during the Cold War. But that view obscures a history of sharp disagreement between the two allies. It is a mythical past that stands in the way of repairing our alliance today. In reality, Korean nationalism and American strategic policy goals have often clashed. Differences over North Korea have arisen repeatedly. And anti-Americanism has been a feature of Korean life for decades.

This was true from the earliest postwar days, in a relationship born out of a fateful and poorly considered decision to divide Korea, after decades of Japanese colonial rule, into American and Soviet zones of occupation. Syngman Rhee, South Korea's first leader, was often at odds with his American backers. Washington feared Rhee would provoke a war with the communist North, even after the end of the Korean War.

Relations with Park Chung Hee, who came to power in a military coup in 1961, were even thornier. Park was a fierce Korean nationalist and, according to a close former aide, uncomfortable with Americans. The two countries collided over North Korea policy, economic goals, human rights and democracy.

In the 1970s, South Koreans developed deep doubts about the durability of the alliance, an uneasiness fed by the Vietnam debacle and the withdrawal of U.S. troops from Korea. Park defied U.S. pressure in declaring martial law in 1972, junking the constitution and jailing leading opposition figures. He launched a secret campaign of influence-peddling and bribery of American congressmen to counter U.S. criticism of his policies.

While Park feared abandonment by the United States, North Korea's Kim Il Sung worried that China, after developing ties to Washington, might sell him out. Thus Park, even though he had been the victim of two assassination attempts by North Korea, reached out to Pyongyang. During high-level talks in 1972, there was a remarkable shared belief that the major powers were the obstacle to Korean reunification.

The most alarming sign of an alliance in crisis was Park's dangerous decision to develop nuclear weapons, made in secret in 1971 after Richard Nixon's withdrawal of one of the two American infantry divisions. According to my research, American officials became alarmed over the seriousness of this effort when a young CIA agent provided evidence of a crude design for a nuclear warhead.

In the spring of 1975, my father, the late ambassador Richard Sneider, sent a top-secret cable to Washington calling for an urgent review of the U.S.-South Korean alliance. Korea was "no longer a client state," he wrote, but was "well on its way to middle power status with ambitions for full self-reliance including its own nuclear potential."

Sneider recommended creation of a new partnership, one more akin to our alliances with NATO or Japan. He also pushed for quiet but tough diplomacy to dissuade Park from heading down the nuclear road. That campaign succeeded finally, but not before my father warned Park that the entire security alliance was jeopardized.

Park was assassinated in 1979 by his own intelligence chief, who claimed to have acted at American instigation. The charge was false, but it remains widely believed in Korea. The perilous state of our alliance reached a peak with the Kwangju uprising against military rule the following year, when hundreds of Koreans were killed by troops deployed with the alleged acquiescence of the United States.

Dispelling the myth of the previous golden era in U.S.-Korean relations does not mean that our relations lacked a foundation of shared interest or that the difficulties we face today are not serious. The gap over how to handle the threat from the North is certainly wider and more evident than in the past. And the democratization of South Korea makes our differences visible and harder to manage.

As policymakers from both countries meet this week, they need to take a deep breath and remember that our alliance survived tremendous stresses in the past. The task before us is not to focus on our divergence but to pick up the challenge left unmet 30 years ago -- to define the basis for a long-term relationship that is durable and reciprocal and that finally sheds the shackles of dependency.