A senior official closely involved with Iraq in the Bush administration told me, “Not only did Maliki not try to do broad power-sharing, he reneged on all the deals that had been made, stopped paying the Sunni tribes and militias, and started persecuting key Sunni officials.” Among those targeted were the vice president of Iraq and its finance minister.

But how did Maliki come to be prime minister of Iraq? He was the product of a series of momentous decisions made by the Bush administration. Having invaded Iraq with a small force — what the expertTom Ricks called “the worst war plan in American history” — the administration needed to find local allies. It quickly decided to destroy Iraq’s Sunni ruling establishment and empower the hard-line Shiite religious parties that had opposed Saddam Hussein. This meant that a structure of Sunni power that had been in the area for centuries collapsed. These moves — to disband the army, dismantle the bureaucracy and purge Sunnis in general — might have been more consequential than the invasion itself.