Christian test for refugees aids ISIS. Ground war in Syria could be a worse hornet’s nest than Iraq.

The attacks in Paris have the potential to be game changers. French Prime Minister Manuel Valls exclaimed, “nous sommes en guerre” (we are at war), and President Hollande told the world that “France will destroy IS.” President Obama announced that the U.S. stands together with France, and Secretary of State John Kerry announced meetings with his French counterpart to determine exactly what form the response will take. Talks of war are in the air, and it has been seized upon by many of the Republican hopefuls, and some Democrats have lent their voice to the jingoist chants. Whichever path of response that we choose, we would do well to make sure that we don’t repeat the disastrous invade-first and think-about-what-happens-next-later mode that produced the Iraqi mess and the resultant ISIS conundrum. ISIS has been successful in recruiting Western Muslims, in part, by framing it as a war between Islam and Christian Crusaders–a reminder of the humiliation, plundering, and rape that accompanied the Crusader’s conquering march to the holy land. Meanwhile, candidate Donald Trump, whose ten hour...