The success is fragile, however. North Korea continues to pursue nuclear weapons. Halting that quest will take occasional Chinese political and economic pressure. Beijing believes Chinese economic progress requires access to the U.S. market. Beijing's bankers don't like the Obama administration's protectionist instincts -- its hard-line generals want to see Obama handle a crisis. For China, the current North Korean tantrum is a marketing tool and diplomatic test. Chinese pressure can be bought -- at a stiff price.

Enter Japan. North Korea's dramatic bullies expect Japan to kvetch then roll over, but -- the uncomfortable point -- suddenly Japan has its own script, one with dark historical echoes for East Asia.

In the first decades of the 20th century, the Japanese empire controlled Korea and swaths of contemporary China. Imperial Japanese forces, organized for offensive strikes, attacked Pearl Harbor and threatened Australia.

Japan's post-World War II constitution forswore offensive capacities but permitted self-defense forces. This century, Japan's Self-Defense Forces, however, have become a potent, high-tech military. The tech includes Aegis destroyers armed with U.S.-made Standard 3 antiballistic missiles (ABMs) and ground-based Patriot PAC-3 ABMs. Two months ago. Japan's Maritime Self-Defense Forces announced that it was authorized to intercept North Korean missiles threatening Japanese land and sea territory.

A defensive action? Yes, but indicative of subtle change. The Japanese are tired of North Korea's nuclear threats and worry that U.S. security promises are no longer rock solid. Barack Obama's opposition to ABMs increases their insecurity. The United States has Aegis ships near Japan and says it would intercept an "aberrant missile." This is measured language, carefully hedged -- but it doesn't fully reassure frightened Japanese.

Japan is slowly acquiring offensive capabilities. Japan doesn't have aircraft carriers, but it has deployed a new "helicopter destroyer" that looks like a lot like a "jump jet" carrier capable of offensive operations. Political support for offensive forces is building. When Pyogyang threw a nuclear tantrum in 2006, many Japanese clamored for "strike" weaponry to destroy North Korean missile sites.

Japan's threat of interception informs China that it faces a strategic choice. Continued North Korean possession of nukes and missiles could lead to a revival of Japanese offensive forces -- something China fears.

And a revived Japanese offensive military certainly isn't in North Korea's script.