North Korea and Iran were both part of Pakistan’s A.Q. Khan nuclear proliferation network, which spread nuclear blueprints and material among its clients until it was exposed by the U.S. a decade ago. In July 2013, a Pentagon report on global missile threats warned that “North Korea has an ambitious ballistic missile development program and has exported missiles and missile technology to other countries, including Iran and Pakistan.” On April 11, 2013, nuclear expert David Albright, president of the Institute for Science and International Security, testified to Congress that given the Iranian-North Korean cooperation on missile delivery systems, the lessons for Iran of North Korea’s work to deploy nuclear warheads on its missiles are “apparent.”

For both countries, versed in dodging sanctions, the illicit networks run through China, Pyongyang’s patron and a hub of illicit procurement. In April the U.S. government offered a $5 million reward for help in apprehending a Chinese national, Li Fangwei, accusing him of running a sanctions-violating international procurement network out of China that has sold Iran both missile and nuclear-related materials. The U.S. has asked China to shut down this network since at least 2006, to no avail.

In February of this year, when Iran’s chief nuclear negotiator and foreign minister, Javad Zarif, returned to Tehran from the first round of Iran nuclear talks in Vienna, one of his first meetings was with a visiting North Korean deputy foreign minister. Iran’s Fars News Agency reported that the meeting was devoted to “bolstering and reinvigorating the two countries’ bilateral ties,” as well as mutually assuring each other of their right to “peaceful nuclear technology.” Less than five weeks later North Korea issued a threat to conduct its fourth test of a nuclear bomb.