Former President George W. Bush described North Korea and Iran in 2002 as members of an “axis of evil.” (Iraq was the third). One inference was that the two were cooperating on nuclear and missile programs. North Korea is known to have exported missiles to Iran and also to have provided it with nuclear technology. North Korea may also have obtained centrifuges from Iran for producing highly enriched uranium. This type of cooperation is believed to have waned as a result of international sanctions.

Vahid Salemi/AP/File
Former Iranian President Mahmoud Ahmadinejad, right, shakes hands with then-president of the Presidium of North Korea's Supreme People's Assembly Kim Yong-nam, during a welcoming ceremony in Tehran, Iran, September, 2012.