Experienced chess players understand gambits. Politicians should, too.
What, exactly, is a gambit? In chess, it's an opening--a sequence of moves at the beginning of a game--designed to entice the opponent to make a move that will leave her in a weakened position. Typically, a gambit involves leaving a pawn vulnerable to capture, but in a location on the board that requires the opponent to cede control of the center squares or to make some other tactical concession. A gambit, in other words, involves baiting a trap and waiting for the opponent to walk right into it.
Terrorist attacks should generally be understood as gambits. They are intended to provoke a particular response that the terrorists believe will benefit them, at least in the long run. The response the terrorists desire is probably the one that, for the victim and the wider audience, is the easiest to rationalize and the hardest to resist. As a rule of thumb, if you don't know what the terrorists are trying to goad you into doing, you might be better off not doing anything rather than choosing to follow your gut.
So, what is it that the Islamic State might want? Let's start with an even bigger conflict in the Middle East--one that draws in a variety of powers that are distrustful of one another. Let's add a more visible presence of French, U.S., and Russian military forces. And then let's add an end to the open door for Syrian refugees.
Why might the Islamic State want these things? Because its appeal is based on two things: first, its ability to provide better governance than the weak and corrupt governments of Iraq, Syria, Libya, or parts of Egypt, and, second, its ability to present itself as the best defender of Islam against an implacably hostile West.
Those who have reflexively called for widening the war in Syria and Iraq on the one hand while excluding Syrian refugees from the United States and Western Europe on the other might do well to learn something about gambits.