Although the 2015 nuclear deal has slowed the Islamic Republic’s own atomic research, it doesn’t prevent Tehran from working with Pyongyang to develop a bomb of its own. North Korea already has the necessary technology, and Iran—thanks to the windfall it received from the deal—has the cash desperately needed by Kim Jong-un. Refael Ofek and Dany Shoham write:
From the 1990s onward, dozens—perhaps hundreds—of North Korean scientists and technicians apparently worked in Iran in nuclear and ballistic facilities. Ballistic-missile field tests [of missiles of North Korean design] were held in Iran. . . . Simultaneous with [the negotiations that led up to the nuclear deal] in 2012 and 2013, a permanent delegation of Iranian missile experts was established in North Korea that supported the successful field testing of a long-range ballistic missile in December 2012. . . .
A delegation of Iranian nuclear experts . . . was covertly present at the third North Korean nuclear test in February 2013. . . . In 2015, information exchanges and reciprocal delegation visits reportedly took place that were aimed at the planning of nuclear warheads. . . .
The two countries have followed fairly similar nuclear and ballistic courses, with considerable, largely intended, reciprocal technological complementarity. The numerous technological common denominators that underlie the nuclear-weapons and ballistic-missile programs of Iran and North Korea cannot be regarded as coincidental. Rather, they likely indicate . . . a much broader degree of undisclosed interaction between Tehran and Pyongyang.
The current Iranian-North Korean cooperation, which appears to be fully active, presumably serves as a productive substitute for the Iranian activities prohibited by the nuclear deal. It enables Iran, in other words, to continue its pursuit of nuclear weapons. If not strictly monitored by the Western intelligence communities, this cooperation might take the shape of conveyance from North Korea to Iran of weapons-grade fissile material, weaponry components, or, in a worst-case scenario, completed nuclear weapons. To an appreciable degree, Iran is simultaneously assisting in the upgrading of North Korean strategic capacities as well.
Read more on BESA Center: https://besacenter.org/perspectives-papers/iran-progressing-nuclear-weapons-via-north-korea/