Under previous names, ISIS was based in Iraq during the reign of Saddam Hussein, before our invasion, though it was going by different names then. It had a base in the north where Saddam used the group to attack the Kurds and it had a cell in Baghdad - the cell that decapitated a Catholic nun and so on there... well before the US invasion. It used using the same network as al Qaeda’s in Europe to plot ricin attacks in Europe - recall the police raid where the British police officer was slain and the group had manufactured ricin cream intended to be smeared all over public access areas. The group under an earlier name also carried out the assassination of US diplomat Lawrence Foley in Jordan - all before the invasion of Iraq. Its training base in Afghanistan was adjacent to bin Laden’s, and members of both groups operated together at times and trained in each other’s camps. The only reason the press got away with not calling the group al Qaeda was because its leader at the time - since assumed room temp- had not sworn the oath to bin Laden. He didn’t swear the oath until after the US invaded Iraq and Saddam Hussein was executed. I would suggest that the reason he didn’t swear the oath to bin Laden until then was because he had already sworn loyalty to another. In any case the lack of a formal oath to al Qaeda leadership gave the press an excuse to maintain the claim “alQaeada” had nothing to do with either Iraq or Iran even if this groups earlier editions did.
This is why so much beheading has emerged as of late and especially the posting of heads in public. These are early chechen tactics from the mid-90's.
I know chechens well.