The quiz is - do targeted killings really improve the situation?
As such, Adnani was probably the most senior casualty that Isil has yet suffered. His death raises a crucial question in counter-terrorism: how much real difference does the elimination of a battle-hardened operative make? Will Isil be weakened by the loss of a man like Adnani, or will his sudden removal by a metaphorical bolt from the blue make no genuine impact?
Those who have been involved in “targeted killings” have agonised over their effectiveness. Ami Ayalon, who led Israel’s Shin Bet security service from 1995 until 2000, eventually reached the emphatic conclusion that assassinations were not worth the moral price.
And yet it seems incontestable that Osama bin Laden’s original al-Qaeda network was gravely weakened by the remorseless elimination of one figurehead after another – including bin Laden himself – at the hands of US drones and commando raids after 2009.
If “core al-Qaeda” is a shadow of its former self, then the heavy toll inflicted by Predators and Reapers is a big part of the explanation.
So why do targeted assassinations damage al-Qaeda but have little effect on the likes of Hamas and Hizbollah? The answer lies in the differing nature of these groups. Rather than being a movement firmly grounded in a society, al-Qaeda was a network, built around individuals with charisma and expertise.
Once those kingpins were toppled by missiles falling from a clear sky, the network around them crumbled. Whatever technical or other expertise the targets had built up over the years proved extremely difficult to replace.
So the question of whether killing Adnani will weaken Isil depends, at root, on whether the movement is closer to al-Qaeda or Hamas. If the tempo of terrorist attacks in Europe does fall in the aftermath of his killing, that will be important evidence that Isil shares the vulnerability of al-Qaeda.