But the sheik’s fortunes began to decline after the last U.S. troops withdrew from Iraq in 2011. Many of the Anbari fighters, known as the Sons of Iraq, were never paid by the Iraqi government, then led by Prime Minister Nouri al-Maliki. What’s more, Sheik Ahmad told me in 2012 that his contacts with the U.S. government stopped after the last troops pulled out. The sheik still publicly aligned himself with Maliki and the central government, even thought that government was failing to provide basic security in western Iraq. These failures by the Baghdad government created the conditions for the...