“Once, during a raid in Ramadi, the GIs rounded up several men from a suspected safe house and forced them to lie face down on the concrete with their hands behind their heads. From inside the house appeared a small boy of about four years. Seeing his father lying on the ground, the boy walked between the rows of prostrate men and, without a word, lay down next to his father, placing his tiny hands behind his head.”

This is a wrenching aside in a book that aims to  explain how Islamic State came to be. It’s clear and well told, a good guide  to the crumbling of Iraq and Syria over the past dozen years.

Black Flags focuses on  Abu Musab al-Zarqawi, the founder of what became al-Qaeda in Iraq and  its vicious new form of terror: beheadings, attacks on Shiite mosques and car bombings whose targets included children. This is the man that al-Qaeda’s second in command, Ayman al-Zawahiri, admonished for harming the organisation’s brand.  

The book tracks  Zarqawi from poorly educated brawler in Jordan to  architect  of a wave of bombings in Baghdad that hollowed out the Bush administration’s declaration of victory in Iraq and lit new waves of hatred there.