Well, it was a very exciting weekend on the Korea peninsula, as South Korea vowed to go ahead with live-fire artillery exercises on Yeonpyeong Island, site of the artillery exchange between ROK and DPRK earlier this month. North Korea vowed to retaliate, the U.N. Security Council met all day yesterday without any agreement on the matter, Seoul recommended island residents go to bunkers, and everyone urged restraint by everyone else.

Very exciting!! How would today's exercise play out? Mark McDonald and Martin Fackler report for the New York Times:

Defying North Korean threats of violent retaliation and "brutal consequences beyond imagination," South Korea on Monday staged live-fire artillery drills on an island shelled last month by the North.

The immediate response from Pyongyang was surprisingly muted, however. A statement from the North's official news agency Monday night said it was "not worth reacting" to the exercise.

"Maybe we had a little impact," said Gov. Bill Richardson of New Mexico, who as an unofficial American envoy was in Pyongyang when the drills ended. Mr. Richardson, a former ambassador to the United Nations, said earlier that the North had offered concessions on its nuclear program, including a resumption of visits by United Nations inspectors.

Wait, that's it? Pyongyang issues threat after threat and then claims the whole thing isn't worth their bother? Let's dig a little deeper into the Times story:

The question now is whether the North will make good on its promises to retaliate, and how it might do so. Mr. Lankov, the analyst, said he did not expect a massive response by Pyongyang because the recent incidents are part of a North Korean "strategy of tensions," meaning that North Korean leaders want to choose when and where to strike.

"I do not think the North Koreans will do much this time," Mr. Lankov said. "They'd rather deliver a new blow later when they will be ready. But the maneuvers still mean a great risk of escalation."

Meanwhile, Mr. Richardson said the North had agreed to concessions related to its nuclear program, a main source of tension on the peninsula. A former United States special envoy to North Korea, Mr. Richardson was on an unofficial trip approved by the State Department. He met with high-ranking military officials, the North Korean vice president and members of the Foreign Ministry over four days.

Mr. Richardson said the North had made two significant concessions toward reopening six-party talks on the country's nuclear program. The North's proposal would allow United Nations nuclear inspectors back into the Yongbyon nuclear complex to ensure that it is not producing enriched uranium for a nuclear bomb. The North recently showed an American nuclear expert a new and stunningly sophisticated facility there. It expelled international inspectors last year.

North Korean officials also told Mr. Richardson that their government was willing to sell 12,000 plutonium fuel rods to South Korea, removing bomb-making material from the North, he said. "I would describe this as important progress," he said of the concessions.

So now North Korea also wants to restart the Six-Party Talks? What just happened? As always, trying to explain North Korean behavior is a challenging task. Here are some possible explanations:

1) North Korea finally got caught bluffing. True, they have the least to lose from the ratcheting up of tensions, but that doesn't mean they have nothing to lose from a military escalation with the ROK. The past month of tensions got everyone's attention, and North Korea is only happy when everyone else is paying attention to them.

2) Kim Jong Un was busy. One of the stronger explanations for the DPRK's last round of provocations was that this was an attempt to bolster Kim the Younger's military bona fides before the transition. Reading up on what little is out there, it wouldn't shock me if he planned all of this and then postponed any retaliation because he'd organized a Wii Bowling tournament among his entourage.

Somewhat more seriously, it's possible that there are domestic divisions between the military, the Foreign Ministry, and the Workers Party, and that the latter two groups vetoed further escalation.

3) China put the screws on North Korea. For all the talk about juche, North Korea needs external aid to function, and over the past year all the aid lifelines have started to dry up -- except for Beijing. As much as the North Koreans might resent this relationship -- and they do -- if Beijing leaned hard on Pyongyang,

4) North Korea gave the ROK government the domestic victory it needed. Bear with me for a second. The shelling incident has resulted in a sea change in South Korean public opinion, to the point where Lee Myung-bak was catching hell for not responding more aggressively to the initial provocation. This is a complete 180 from how the ROK public reacted to the Cheonan incident, in which Lee caught hell for responding too aggressively.

Lee clearly felt domestic pressure to do something. Maybe, just maybe, the North Korean leadership realized this fact, and believed that not acting now would give Lee the domestic victory he needed to walk back his own brinksmanship.

5) Overnight, the DPRK military hired the New York Giants coaching staff to contain South Korean provocations. Let's see... a dazzling series of perceived propaganda victories, followed by the pervasive sense that they held all the cards in this latest contretemps. Then an inexplicable decision not to do anything aggressive at the last minute, after which containment policies fail miserably. Hmmm… you have to admit, this MO sounds awfully familiar.

If I had to make a semi-informed guess -- and it's just that - I'd wager a combination of (1) and (4).

Alternative explanations welcomed in the comments.