Not only is the Iraqi army badly run and demoralised, it is up against an insurgency that has already proved one of the most lethal in the world, having held its own for nearly a decade against the US military. While the odd US air strike might help the Iraqi security forces a bit, the most they might hope for is retaking Tikrit, a relatively small place. Mosul seems out of the question, as do Fallujah and Ramadi to the west, which Isis seized five months ago and has successfully defended ever since. To put this in a British context, it's the rough equivalent of London losing control of Birmingham and the Midlands plus Bristol and the West Country, plus many towns in between. In effect, a new state is being carved out, broadly along the lines of Iraq's Sunni Muslim heartlands, where Sunnis will be free from the writ of the Shia-led government that they say treats them as second-class citizens.