Suppose intelligence discovered that a terrorist organisation was planning a fresh atrocity that would shock the world, but had no further leads to prevent it. Then it might be appropriate to take the longest of shots – send an agent into Iraq to infiltrate that organisation at a senior level, in the hope that the secret is shared with him.
So it happens that Mike Martin, a veteran of the war in Afghanistan, is sent to impersonate The Afghan (Izmat Khan), a war hero supposedly returned from prison in Guantanamo. He is accepted as a member of the Taliban, thanks to his genuine background from growing up in the region and intensive coaching on the religion and customs of the area. But the real mission is to learn about the planned atrocity and to intervene.
It’s a clever plot, if necessarily far fetched – I’d read the book some years ago and it was good on re-reading.