CISAC's Martha Crenshaw writes in Foreign Policy that the Obama administration has been vigorously criticized for a hesitating, inconsistent, slow, and confused response to the deadly attack on the consulate in Benghazi. But the record suggests that hesitation may be more the norm than the exception. Difficulty in attributing responsibility for terrorist attacks has always been an obstacle to responding effectively -- no matter how strong the desire to do so. Attribution needs to be both timely and credible, but these two requirements are often incompatible. It takes time to identify the perpetrators -- and, even then, history shows that it's not always possible to bring them to justice.