If there was any doubt North Korea had mastered the capacity to build nuclear bombs, it has been removed. We have clarity.

The effect of North Korea’s forced entry into the nuclear club, joining the United States, Russia, Britain, China, France, Israel, India, and Pakistan, may be as far-reaching as was Moscow’s entry in 1949.

For Kim Jong-Il now has the ability to smuggle nuclear devices in the cargo holds of merchant ships into U.S. ports, or sell atom bombs to friendly nations like Iran. He will soon be able to launch missiles with nuclear warheads onto U.S. forces on the DMZ and Okinawa. Given time and the testing of his long-range rockets, North Korea will one day be able to bombard the American mainland with atom bombs.

Any such attack would of course entail the annihilation of his military and regime. Nevertheless, Pyongyang now has a credible deterrent to U.S. strikes on its nuclear facilities.

In his 2002 State of the Union, George W. Bush issued a clear ultimatum to Iraq, Iran, and North Korea, the “Axis of Evil”: The United States will not allow the world’s most dangerous regimes to acquire the world’s most destructive weapons. The Bush Doctrine has been defied by Kim Jong-Il.

What do we do now? To quote President Lincoln, as our situation is new, so we must think and act anew.

U.S. forces on the DMZ are now as much hostages to the North Korean military as they are defenders of the South. It is less credible today than yesterday that America would launch any preemptive strike on North Korea  with our forces in Pyongyang’s nuclear gun sights.

It is also impossible to believe the United States, its forces stretched thin by Iraq and Afghanistan, would send another army of a third of a million men to fight a land war with North Korea, as we did over half a century ago. Why, then, do we keep an army in South Korea?

The only rationale is to ensure that Americans are killed in any North Korean invasion, and, thus, that the United States will bring the full force of its air and naval power against Pyongyang in any such war.

But why should we maintain an indefinite commitment to fight a war for South Korea, when the result could now be escalation involving nuclear strikes on U.S. forces in the Pacific or the American homeland?

For over a decade, this writer has argued for a withdrawal of all U.S. forces from South Korea  because the Cold War was over, the Soviet Union had broken up, and there was no longer any vital U.S. interest on the peninsula. And because South Korea, with twice the population of the North, an economy 40 times as large and access to U.S. weapons generations ahead of North Korea’s 1950s arsenal, should defend herself.

If we leave now, however, Seoul will take it as a signal that we are abandoning her to face a nuclear-armed North.

South Korea will have little choice but to begin a crash program to build her own nuclear arsenal.

Yet, as the United States cannot be forever committed to fight a nuclear-armed North Korea to defend South Korea, a nuclear-armed South is probably in the cards. Pyongyang’s explosion of Monday is probably already forcing second thoughts in Seoul about the necessity of developing its own deterrent.

China is said to be enraged that North Korea has defied it by detonating a nuclear device. Beijing should be. For the Chinese-Russian monopoly on nuclear weapons in North Asia has been broken. And the democracies there are unlikely to endure a situation where they can be subjected to missile and nuclear blackmail by a backward, bellicose little dictator like Kim Jong-Il.

Japan, a nation of 125 million, with the second-largest economy on earth and the technological equal of any nation, will not allow itself to be blackmailed by this former colony of 20 million impoverished Koreans.

In securing her against any threat from Russia or China in the Cold War, Japan relied on the U.S. nuclear umbrella. But will Japan be willing to rely on America, and forego her own nuclear deterrent, if she is threatened by a rogue state like Kim Jong-Il’s?

If all three of Japan’s closest neighbors  Russia, China, and North Korea  have nuclear weapons, and U.S. power is receding in Asia, and American will is being severely tested in Afghanistan and Iraq, Tokyo will surely have to reconsider the nuclear option.

Beijing refused to use its enormous economic leverage to coerce North Korea into giving up its nuclear program. Now, China may find herself with a nuclear-armed South Korea, Japan, and perhaps Taiwan.

As for the United States, the nuclearization of Asia means it is time to move U.S. forces back to Guam and, as LBJ said, let Asian boys do the fighting that Asian boys should be doing for themselves.