For North Korea, the incentive to transfer technology, or an actual bomb, in exchange for money, or whatever else the regime needs, is powerful. The only world power capable of discouraging them from proliferating is China, but the Chinese are not going to push much harder than offering stiff rhetoric. The Chinese don’t necessarily want North Korea to have a bomb, but what they fear even more is destabilizing their neighbor such that the regime falls, the Korean peninsula is reunited, and they wind up with a pro-American government hosting 50,000 U.S. troops on their border. Beijing prefers to have a buffer.

Pyongyang’s nuclear program is the crown jewel of the North Korean state enterprise, a carefully guarded secret to which they have given only Iran access. Given how extensively the Iranian nuclear program has been penetrated by foreign intelligence services—which foreign minister Ali Akbar Salehi openly admitted in 2010—the North Koreans surely understood they were taking an enormous risk by letting Iranians in the door. Whatever they’re getting from Iran in exchange—oil, money, or scientific cooperation on complicated issues—must be crucial. If Tehran has paid for access to Pyongyang’s program, it will also pay for a bomb. At this point, it could be only a matter of haggling over the price.

“Some of us have been saying this is something to worry about for five or six years,” said Henry Sokolski, executive director of the Nonproliferation Policy Education Center in Washington, D.C. “The North Koreans have been cooperating with Iran for about a decade on nuclear and missile issues, and the Iranians have several full-time weapons engineers on site in North Korea. Neither the North Koreans or the Iranians have made a secret of this. The Iranians were reported at North Korea’s last nuclear test as well. It’s hard to believe they had no access to the most recent test.”