Pulitzer Prize-winning reporter Joby Warrick reveals how the strain of militant Islam now raising its banner across Iraq and Syria spread from a remote Jordanian prison with the unwitting aid of American military intervention. When he succeeded his father in 1999, King Abdullah of Jordan released a batch of political prisoners in the hopes of smoothing his transition to power. Little did he know that among those released was Abu Musab al-Zarqawi, a man who would go on to become a terrorist mastermind too dangerous even for al-Qaeda and give rise to an Islamist movement bent on dominating the Middle East. Zarqawi began by directing hotel bombings and assassinations in Jordan from a base in northern Iraq, but it was the American invasion of that country in 2003 that catapulted him to the head of a vast insurgency. By identifying him as the link between Saddam and bin Laden, the CIA inadvertently created a monster. Like-minded radicals saw him as a hero…