And we thought the hysteria over the sequester was bad. North Korea continued its policy of brinksmanship today over new sanctions applied after a third illegal nuclear-weapons test by claiming it has put its artillery forces in their highest alert status:

North Korea’s military warned Tuesday that its artillery and rocket forces are at their highest-level combat posture in the latest in a string of bellicose threats aimed at South Korea and the United States. … On Tuesday, the North Korean army’s Supreme Command said it will take “practical military action” to protect national sovereignty and its leadership in response to what it called U.S. and South Korean plots to attack. The statement, carried by the North’s official Korean Central News Agency, cited the participation of nuclear-capable B-52 bombers in South Korea-U.S. drills. North Korea’s field artillery forces — including strategic rocket and long-range artillery units that are “assigned to strike bases of the U.S. imperialist aggressor troops in the U.S. mainland and on Hawaii and Guam and other operational zones in the Pacific as well as all the enemy targets in South Korea and its vicinity” — will be placed on “the highest alert from this moment,” the statement said.

This latest threat may have been prompted by something other than the sanctions. The US announced yesterday that it had signed a pact with South Korea on Friday that lays out with specificity what role US and Republic of Korea forces will play in the event of an attack from the North:

Washington’s mutual defense treaty with South Korea obligates the American military to fight to defend its ally if a war breaks out on the Korean Peninsula. The deal, signed Friday, defines what role the United States would play in dealing with what South Korean military officials called “local” provocations from the North, such as its shelling of a border island in 2010, which killed four South Koreans. The two allies said they had been working to improve their contingency plans ever since. They called the contingency plan “South Korean-led, U.S.-supported.” It laid out various types of localized North Korean provocations and a joint South Korean-American response to each of them, South Korean officials said. By putting the allies’ combined commitment on paper, the agreement will help serve as a deterrent against North Korean provocations, they said. But the two allies refused to disclose more details on such sensitive and potentially volatile questions as how far the United States would go in its supporting role, especially at what point American troops would directly join a South Korean counterattack against a North Korean provocation. In recent weeks, South Korea has said that if provoked, it would attack not only the origin of the North Korean provocation but also “its supporting forces and its commanding post.”

In other words, no one’s going to assume that a conflict erupting on the border or in the Yellow Sea is just an accident any longer. The US and South Korea are both warning Pyongyang that it will react as though the DPRK intends to open a wider war in those circumstances, striking back not with corresponding force but with overwhelming force. Over the last several decades there have been a number of these hot flashes in a cold war, but most of them have remained single-incident flashes that ended quickly and without engaging wider forces. Thanks to the rhetoric and the actions of Kim regime, those safety valves now appear to be off the table.

And now that Kim Jong-un has climbed out onto that limb, he may have no choice but to follow through:

The North’s recent threats are seen partly as efforts to strengthen internal loyalty to young leader Kim Jong Un and to build up his military credentials. Kim “needs to show he has the guts. The best way to do that is to use the military might that he commands,” said Lee Yoon-gyu, a North Korea expert at Korea National Defense University in Seoul. “This paves the way for greater praise for him if North Korea makes a provocation later and claims victory.” Kim will eventually be compelled to do “something provocative to prove the threats weren’t empty,” Lee said.

Today, by the way, is the third anniversary of one of the most recent flashpoints in this standoff — the sinking of the Cheonan, which took the lives of 46 South Korean sailors. Aside from an artillery barrage a few months later, that was the final high point of Kim Jong-il’s reign as hereditary dictator. Kim Jong-un might be under pressure to prove himself the equal of his father, but if he does, the peninsula could blow wide open.