A political strategy to deal with ISIS is thus ultimately likely to mean negotiations with the core leadership, however much we despise the group’s methods. It may seem outlandish that a creed as absurd as ISIS’s should enjoy political support, but on the other hand, it is very hard to see how 2,000 fighters were able to take the Iraqi city of Mosul, population about 1.5 million, without it. And any political strategy will need to address the sources of this support—particularly Sunni alienation. In Iraq, a major cause of this was the corrupt and sectarian rule of Nouri al-Maliki’s Shiite-dominated government in Baghdad, which made even ISIS seem preferable among some Sunnis. It’s no coincidence that the self-styled Islamic State caliph Abu Bakr al-Baghdadi draws many of his deputies from among former officers in Saddam Hussein’s army and members of the Baath party. It is less likely that those individuals have suffered some sudden genuine conversion to an extreme sect of Islam than that they see an opportunity to fight the Shiite majority that has ruled the country since the fall of Saddam’s minority Sunni-dominated regime. In Syria the domination of the Assad family and their Alawite backers have had much the same effect on Sunnis there. There are, in other words, genuine grievances underlying ISIS’s resilience in Mesopotamia.

Who should be talking to ISIS? Like the Taliban in Afghanistan—who have been in on-again, off-again talks with the U.S. government for several years—they are likely to want to talk in the first instance to those who are fighting them, in other words the Americans and their allies, not least since they do not accept the legitimacy of governments in Baghdad and Damascus. Their immediate aim will be to reduce the military pressure they face. It should ultimately be legitimate governments in Iraq and Syria—which in the latter’s case will almost certainly require the removal of Bashar al-Assad—that work with Sunnis to determine their place in society, perhaps through the creation of autonomous Sunni regions comparable to the Kurdish Regional Government in Iraq. In the same way, the Afghan government will be the Taliban’s interlocutor if and when peace talks finally take off in Afghanistan.

What is there to talk about with such a horrific and fascistic group? For one thing, it is important to understand that talking with terrorists is not the same as agreeing with them.