The earth rumbled beneath the Korean peninsula on Jan. 5, signaling an underground nuclear test by North Korea. Pyongyang claimed to have set off its first hydrogen bomb, but experts looking at seismographs saw evidence of a much smaller explosion — likely the country's fourth atomic bomb test since 2006. Possibly, it was an atom bomb boosted by additional nuclear material.

H-bomb or A-bomb, the impact is clear: a nasty reminder that one of the world's most isolated regimes poses a great danger.

There's a clockwork-like predictability to North Korea's belligerence and brinkmanship: Every so often — just when the world seems focused on other crises — the North ratchets up tension by testing a bomb or ballistic missile.

So what do we have to show for decades of patience with North Korea? Um, four nuclear tests.

The Obama administration actually has a name for it: "strategic patience." The idea is to wait out the North, using subtle pressure to coax it back to the negotiating table to strike a grand bargain on its nuclear program.

So what do we have to show for decades of such "strategic patience" with North Korea? Um, four nuclear tests — and some ballistic missile tests, too.

This is the problem with endless patience and wandering attention.

In North Korea's alternate reality, testing an "H-bomb of justice" is needed to fend off "a gang of cruel robbers" — the United States.

Waiting around for North Korea to change is folly. The country, bumping along in poverty and always at risk of famine, has an apparently limitless capacity to endure hardship. North Koreans don't know any better. The Kim family designed their country that way.

There is, however, one untapped vulnerability. A Congressional Research Service report has said it plainly: Food and energy aid from China is "an essential lifeline for the regime."

China's main worry is preventing the collapse of North Korea, which could cause a refugee crisis on China's border. Just as bad, from China's vantage point, would be for the North to be absorbed by South Korea, a key American ally.

Still, there are signs Beijing may be frustrated with Kim Jong Un. Beijing knows that the more Kim stirs up trouble, the more active the U.S. will get in defending the Pacific, tightening ties along the way with South Korea and Japan. That threatens to hem in China.

Relying on China to protect American interests shouldn't be at the top of anyone's list; but with four nuclear tests in the bag, it's time for the U.S. to replace "strategic patience" with some urgency. Let's find out if China is ready to push North Korea into serious talks.

The U.S. cannot allow other issues to distract from the threat of nuclear North Korea. The next bomb Pyongyang detonates in a test could be big enough to truly frighten the world, or small enough to place on an intercontinental ballistic missile.

REPRINTED FROM THE JACKSONVILLE DAILY NEWS

Photo credit: SDASM Archives