“The existence of the state is very important to Isis’s global ideological appeal,” said JM Berger, author of Isis: The State of Terror. “Eliminating the state would likely undercut a lot of Isis recruitment and that of some of its branches in other regions.”

The Paris attacks and the bombing of a Russian passenger jet in Sinai came as that territorial expansion stalled and in some places reversed, in the face of pressure from a diverse range of enemies, from Kurdish militias backed by US bombs to Syrian troops with Russian support.

The killings might have been intended as a show of strength, a new recruiting tool for those drawn to horror, or a demonstration that Isis has the ability to punish countries trying to dismantle its rule of terror – even as it puts its “caliphate” in some jeopardy.

The group’s leaders would have known that if the Paris attackers’ plans succeeded, that would bring a greater focus and ferocity to airstrikes and would be likely to increase the flow of weapons and other support to groups that are fighting Isis on the ground.