The Islamic State of Iraq and Syria, or ISIS, smashed its way into the world’s consciousness earlier this month when it seized Mosul and the Beiji oil refinery in Iraq. Starting last fall, ISIS began imposing its theocratic rule over a wide swath of Syria, then quickly wrested control of the emblematic Iraqi cities of Fallujah and Ramadi. With the more recent attacks, it menaced the government in Baghdad; it also forced President Obama to reengage with a war from which he thought he had extricated the United States.
In trying to explain ISIS’s rapid success, alarmed observers have pointed to the extreme tactics that drew condemnation even from Al Qaeda: mass executions, beheadings, and crucifixions. Some see local conspiracies, believing Arab governments allowed the group to grow in order to justify their own heavy-handed crackdowns. Others suggest that Shi’ite Iran indirectly funded the movement as part of its own strategy to divide the Sunnis from within.