ISIS is murdering and enslaving across Syria and Iraq. Russia is deploying dozens of aircraft to support the regime in Damascus. Huddled masses have been tempest-tossed into Europe. At the eye of the storm, Bashar al-Assad is pursuing a cynical, brutal, and risky strategy to cling to power.

Assad’s plan, it seems, is to deliberately aid the rise of ISIS—what I call the devil’s gambit. The logic is simple and ruthless: radicalize the opposition so that the Syrian dictator looks like a lesser evil to domestic and foreign audiences. Here, Assad benefits from the inherently polarizing nature of civil war, as a cycle of atrocities and revenge pushes all sides to the extreme. He has further spurred radicalization by focusing the regime’s fire on moderate enemies, while reportedly releasing jihadists from jail and purchasing oil from ISIS. In recent months, the Syrian military allegedly used air strikes to help ISIS advance toward the city of Aleppo. Khaled Khoja, a Syrian opposition leader, claimed that Assad’s fighter jets were acting as “an air force for ISIS.”

In the widening gyre, the center cannot hold. Back in 2011, the relatively moderate Free Syrian Army seemed a plausible candidate to lead the resistance against Assad. Now the leading rebel factions include ISIS, the Islamic Front, and the al-Nusra Front, which is affiliated with al-Qaeda. The U.S. effort to train a moderate Syrian force has proved to be a pitiful and quixotic quest. After 10 months and millions of dollars, the United States has created a rebel army that is five strong. Not 5,000 strong, or 5 percent of the opposition. But literally five guys—barely enough to run a burger joint.

The tyrant and the terrorists have a symbiotic relationship. While ISIS rails against the secular regime, its focus is on building the caliphate, not getting rid of Assad. Meanwhile, ISIS’s advance in Iraq in 2014 was a godsend for the Syrian regime. The insurgents headed away from Damascus. And the group’s capture of the city of Mosul and much of Anbar province terrified the West. A reluctant Barack Obama could not accept the fall of Baghdad, and authorized extensive air strikes against ISIS.

For both Western countries and Assad’s Alawite constituency at home, the choice is stark: the devil you know, or…