The bottom line on whether Iran tried to build nuclear weapons

The investigation into the world’s worst-kept secret, Iran’s nuclear weapons program, has been officially and formally closed. The United Nations’ nuclear watchdog, known as the International Atomic Energy Agency (IAEA), voted on Tuesday, to close its years-long investigation into whether Iran ever tried to work on a nuclear weapon. The answer, to virtually no one’s surprise, was yes.

Iran has long denied that it ever worked on nuclear weapons — which would have violated international law — despite overwhelming evidence to the contrary. This put the Iran nuclear talks in a pickle: The world wanted an accounting of what Iran worked on, and what the country did and did not accomplish, so as to understand the program and how to monitor and contain it. But Iran didn’t want to admit guilt, and it didn’t want to let inspectors poke around its sensitive military facilities.

The compromise they worked out is this: Iran caved on inspections and on letting the IAEA investigate. But the nuclear deal could not go into full force until the IAEA declared that it had fully investigated the question of old nuclear weapons work. The IAEA issued its report on that earlier this month, and on Tuesday it voted to formally close the investigation. It declared it was satisfied it knew enough.

So what did the IAEA find? What did the years-long, formal investigation into Iran’s alleged nuclear weapons program find? Nuclear weapons expert Andreas Persbo, writing at Arms Control Wonk, summed it up in one very careful, precise paragraph:

A careful examination of the Director General’s report should lead the reader to conclude that Iran, over the past 20 years, made some considerable progress towards nuclear weapons acquisition, but that the country still had some way to go. Most development activities ended in 2003. Iran dabbled in computer modeling of nuclear weapons designs up to 2009 after which this work appears to have stopped as well. In any case, the Agency notes that this work was “incomplete and fragmented.”

This is mostly in line with what the world already knew. A 2007 National Intelligence Estimate (a formal report by US intelligence agencies) suggested that Iran had worked on a nuclear bomb program before 2003 but shut down the program that year. The IAEA investigation mostly confirms that, but does add that Iran also did some minor work on bomb-related computer modeling between 2003 and 2009.

In other words: Iran used to have a nuclear weapons program, which violates international law, but shut it down some years ago and no longer has any such program.

So what’s the upshot of all this? According to Jeffrey Lewis, a nuclear proliferation scholar who writes at Foreign Policy, it means we have further confirmation of Iran’s long-suspected nuclear weapons work, and we learned a bit more about the program in ways that will make future activities easier to monitor, but beyond that this doesn’t change much.

“Closing the file does not mean that Iran is no longer subject to unusual scrutiny by the IAEA. Quite the opposite,” Lewis writes. “The IAEA is not packing up and going home. It is moving in.”

The big significance here is that the world has cleared one of the toughest and last remaining hurdles to implementing the Iran nuclear deal, which comes with restrictions as well as inspection and monitoring regimes that last 10 to 25 years.