Washington Two big questions hang over the new agreement to contain North Korea's nuclear weapons program at its current level - whatever that level is.
Why has a secretive government addicted to power politics and flexing its military muscles abruptly turned to negotiations and peaceful compromise?
And why is North Korea doing the same?
The Bush administration of course cannot match Kim Jong Il's regime in paranoia, bellicosity and information control, although this White House seems at times to have been tempted to try. Other countries know next to nothing about Pyongyang's motivations, intentions or even its ability to carry out any agreement it makes.
This deepens the Washington end of this great strategic mystery: Why is President Bush accepting the promises of a regime he has regularly excoriated - at a time when officials in his administration make a credible case that North Korea has just been caught helping Syria with nuclear technology?
North Korea's desperation as its economy implodes and its people starve is clearly part of the answer. Pyongyang's plight has helped U.S. negotiator Christopher Hill get an agreement that he feels can be verified and enforced. Timing is also everything for Bush, who reaches for diplomatic successes before his presidency ends.
There are months of quibbling ahead over the differences between "disabling" and "dismantling" North Korea's plutonium production facilities and other points in the agreement. But Hill appears to have pulled the hermit nation of North Korea into an international process that carefully calibrates risks and rewards on both sides.
A crucial provision of the six-nation accord announced in Beijing on Wednesday requires Pyongyang to declare the extent of its weapons-grade plutonium stockpile, including the amount it used in a nuclear test last year.
U.S. officials have estimated that North Korea could make 10 to 12 bombs from its existing stockpile. But the actual number is smaller - perhaps half as much - according to the intelligence service of one major Asian nation. A significant revision downward in U.S. intelligence estimates of North Korea's nuclear threat could explain the Bush administration's more relaxed view of Pyongyang in recent months.
But the more significant change in attitude has come from Pyongyang toward Washington, according to diplomats involved in the talks, which also included China, Japan, Russia and South Korea.
A key moment came when North Korea agreed to an international inspection in September to determine how its main nuclear complex at Yongbyon should be disabled - and asked Hill to have the United States rather than the United Nations carry out that intrusive inspection.
A U.S.-led inspection would have much more credibility in Washington, the North Koreans indicated. They also want to move quickly - that is, while Bush is still in office and can presumably beat back Republican opposition to the agreement.
At Hill's suggestion, the inspection team was broadened to include experts from China and Russia, the other nuclear powers represented in the talks, to spread the mission's responsibilities and risks. The inspectors' report cleared the way for the comprehensive package of requirements and incentives unveiled in Beijing.
In another bout of tacit cooperation that indicates this deal may be serious enough to last, the United States and North Korea have kept the agreement from being derailed by the mysterious airstrike that Israel staged into Syria on Sept. 6. Israel and Syria have both thrown unusual secrecy around the raid, refusing to disclose what was hit.
But highly classified U.S. intelligence reports say that the Israelis destroyed a nuclear-related facility and caused North Korean casualties at the site, which may have been intended to produce plutonium, according to a senior official with access to those reports. The Israelis have given the United States photographs, physical material and soil samples from the site - taken both before and after the raid - according to two independent sources.
A last gasp of North Korean international banditry before going straight on nuclear nonproliferation? A continuing confidence by Pyongyang that it can say one thing in public and do another covertly? Or simply the serendipity of one branch of a secretive government going about its skullduggery while others go a different way?
With North Korea, it is of course unclear. Winston Churchill's famous description of Russia - a riddle wrapped in a mystery inside an enigma - would be mere understatement if applied to Kim Jong Il's regime. That is why it is both good and important that Christopher Hill has put such emphasis on transparency in this agreement. Who knows? It may even catch on in Washington.