Thought experiment: what if the Iran nuclear deal had failed?

Even after the Iran nuclear deal was formally implemented on Saturday, debate continues, and will likely continue for some time, over whether it was worth striking or whether it was, as Israeli Prime Minister Benjamin Netanyahu deemed it, a “historic mistake.”

The debate has always turned on a counterfactual: “If not this deal, then what?” Critics argue that Obama administration officials could have gotten a better deal if they’d just tried harder, been tougher on Iran, or waited longer. Supporters say the alternative wouldn’t have been a better deal, which was not achievable; it would have been no deal, and possibly war.

It’s always difficult to argue a counterfactual, but it’s useful to consider what things might look like today if we hadn’t gotten the nuclear deal with Iran. Historian and scholar Graham Allison has done just that, writing at Harvard’s Belfer Center for Science and International Affairs, where he is the director. (Allison is best known for his book on the Cuban Missile Crisis.) That doesn’t mean he must therefore be right, but it’s worth at least considering his view.

Here’s what Allison thinks likely would’ve happened if we hadn’t passed this nuclear deal:

The international community would have concluded that the U.S. government had become so paralyzed that it was unable to play any consistent role in the world. The international sanctions regime would have collapsed, with Russia, China, India, and most likely a number of European nations resuming trade and investments with Iran.

Iran would have restarted the activity it froze during negotiations: enriching uranium, adding to its stockpile of six bombs-worth of nuclear material, installing additional centrifuges, and continuing construction on its heavy water reactor.

This activity would continue shrinking Iran’s “breakout time” — the time required to produce enough nuclear material for one weapon—from the two months at which it had been frozen to one month, or one week, or closer. Israel’s prime minister would be threatening to attack Iran—and seeking to push the U.S. into taking the lead. Republican candidates for president would be attacking President Obama for having failed to prevent Iran’s acquiring a bomb.

In sum: the world could well have been on the brink of a third major war in the Middle East. So while the nuclear agreement does not resolve all the substantial differences between the U.S. and Iran, it does put what would have been the overriding international challenge of 2016 in a box for the next 15 years.

In other words, if the Iran nuclear deal hadn’t happened, Allison believes international pressure against Iran would’ve fallen apart and Iran would’ve restarted its nuclear program. Eventually, with diplomacy suddenly a much less feasible option, either Israel or the US, or both, may have felt compelled to use military force to stop the program.

So instead of the world we have today, where Iran has taken major steps toward dismantling its nuclear program, Iran could be even closer to the bomb and we could be on the brink of yet another disastrous war in the Middle East.

It’s impossible to know for sure what would’ve happened if the Iran nuclear deal had failed, but the fact that Iran is now further away from having a nuclear weapon than it was before the deal, and that this was accomplished without military force, is probably a good thing.