Britain and the West must brace for reprisal terror attacks by Isil after a string of battlefield defeats in Iraq and Syria, say military commanders.
More than 18 months of air strikes have begun to weaken Islamic State of Iraq and the Levant, meaning it may hit out overseas to show its power, Colonel Steve Warren, US Army spokesman for the anti-Isil coalition, said yesterday (Monday).
His warning came as the US and Russia announced that a long-expected ceasefire in the Syrian conflict would begin on Saturday. Questions remain, however, over whether the agreement, which does not include Isil, can be implemented on the ground.
Isil is now "beginning to lose and we see them in a defensive crouch", Col Warren said in an assessment of the campaign to roll back Isil's advances across Syria and Iraq in 2014.
But he admitted the militants had so far been able to recruit fighters as fast as they had been killed and said the coalition is "not going to kill our way out" of the crisis.
However, coalition commanders were beginning "to see the fraying around the edges of this outfit" as they "begin to crack underneath this pressure", he said, referring to the air campaign and moves to cut off funding.
Intelligence assessments suggest Isil could respond with Paris-style terror attacks on the West. Col Warren said that as the coalition continues to "squeeze this enemy," it could hit back in desperation.
"They are going to want to show the world that they are still viable and one of the ways that they could do that is through a high visibility attack outside of their so-called caliphate," he said.
Col Warren said he had no intelligence about a specific threat, but it was "something we are aware of, this is something that through our various intelligence communities, we are discussing amongst nations". He added: "We do not view a Paris attack or a San Bernardino attack as a sign of strength as many have interpreted it. We view it as exactly the opposite."
Col Warren warned British citizens considering travelling to join Isil that they would likely die.
"You will either be killed by your so-called partners, who have executed each other with grotesque regularity, or you will be killed by ground forces in Syria or Iraq, who don't want you there, or if you manage to survive either of those two things, you will be killed by coalition air power," he said.
Col Warren said the drone campaign to kill Isil leaders and high-profile figures such as Mohammed Emwazi, the British Isil executioner known as Jihadi John, had sown paranoia within the movement's ranks and led to a purge of suspected informers.
Disillusion and a realisation among would-be jihadists that "this caliphate isn't all unicorns and rainbows'', has hit recruitment, he said.
However, Shashank Joshi, a research fellow at the Royal United Services Institute, a London-based security think tank, said the overall picture "is more balanced" than the coalition's positive assessment of its success.
He said coalition gains had so far been "plucking the low-hanging fruit", but it would take years to defeat Isil and the jihadists could easily spring up elsewhere.