Allied airstrikes, including those carried out by British warplanes, have killed more than 6,000 fighters since September, including more than half the militants serving on ISIS’ ruling council.

Among the dead jihadis is Abu Muslim al-Turkmani, a former Iraqi army lieutenant colonel considered Baghdadi’s number two and ISIS’ most senior militant in Iraq.

His death and that of as many as nine others on ISIS’ 18-man leadership council have forced Baghdadi to promote local warlords to the status of regional commanders, as his inner circle of trusted advisers and battle-hardened loyalists becomes increasingly small.