When would a North Korean attack provoke US military response?

The Air Force on Tuesday indicated its willingness to respond to North Korean aggression if it is called upon to do so, even as the Pentagon seemed reluctant to send any signal that might ratchet up tension after the latest North-South conflagration left two South Korean marines dead and more than a dozen others wounded.

Still, while the commander of US forces in South Korea declined to raise the alert level of US service members there, some US military officials were nonetheless tasked with double-checking that all US supplies and troops in the region are at the ready should they be needed.

In a message to some 28,000 US troops in the Demilitarized Zone of the Korean Peninsula, Gen. Walter Sharp maintained a measured tone, assuring soldiers that the barrage of North Korean artillery shells that hit the South Korean island of Yeonpyeong Tuesday “is isolated to the Northwest Island area.”

North and South Korea are still technically at war, because the Korean conflict ended in a cease-fire rather than a truce.

With its hard line, an unpredictable ruler, and a penchant for provoking international outrage, North Korea has long baffled the Pentagon, which seemed Tuesday at a bit of a loss over how to handle the latest confrontation, widely considered the most serious in years.

As Defense Secretary Robert Gates made his way back from a trip to South America late Monday night – just before he learned of the news – he was fielding questions from reporters on the trip about why North Korea was still pursuing its nuclear enrichment program.

Mr. Gates jokingly replied that regarding any “why” questions involving North Korea, his answer is generally simple: “I don’t know.”

North Korea, for its part, promptly claimed that South Korea started the artillery exchange by firing first. It’s a claim likely to be viewed with skepticism in the international community, particularly coming on the heels of the March torpedoing of the South Korean warship Cheonan by North Korea, which killed 26 sailors.

Air Force Chief of Staff Norton Schwartz reiterated Tuesday that Air Force assets are “at a number of places” around the Korean Peninsula. Those assets “are certainly ready” and the regional US military commander is “prepared to use those assets if required,” General Schwartz added.

US military officials, for their part, stepped away from the suggestion that the United States would consider placing tactical nuclear weapons in the region – a suggestion that seemed to come out of South Korea earlier this week on the heels of yet another apparent step forward in North Korea’s nuclear weapons program.

Schwartz added that any use of tactical nuclear weapons would need to be debated “at the highest levels of government.”

To date, there has been no discussion “whatsoever by the joint chiefs” on the subject, he added.

Yet the incident, allowed a Pentagon spokesman, “certainly increases tensions on the peninsula.” South Korea, for its part, put its troops on high alert.

In the meantime, Gates was scheduled to speak with his South Korean counterpart Tuesday.

“At this point, it’s premature to say that we’re considering any military action,” said Col. Dave Lapan, Pentagon spokesman. He added: “Any incident like this we view with concern.”

At what point do actions by the North Korean government require a US military response? That, said Lapan, “remains to be seen.”