The biggest imponderable concerning the war on terror is whether the American people and their leaders are clear on a central question: Exactly who is the enemy in this war? We are, after all, not fighting some abstraction called "terror." The truth is we are engaged in a death struggle with people who use terror — usually involving the deliberate murder of innocent civilians — as an instrument to advance their agendas.

As to precisely who those people are, the past twenty-five months have brought to light a bewildering array of terrorist organizations pursuing a variety of stated objectives, usually with help from this or that rogue state-sponsor. But one thing should be clear post-9/11: The most determined, numerous and dangerous of these enemies are radical, violent Muslims known as "Islamists." [...]