Let us remind ourselves, lest we forget: this is an enemy that operates in the shadows while telling us exactly what their intentions are. An enemy that cannot be negotiated with, reasoned with, or deterred. An enemy that believes nothing short of conquering the Western world will do. An enemy that beheads people as an average day at the office. An enemy that believes the Christian, Jew, and non-Muslim (and the "bad" Muslim too) is an infidel who needs to be converted to "real" Islam, or killed.
Their objective is to have radical Islam dominate the world, and they will stop at nothing to get there. They try to undermine our will to fight back, by killing us, killing our troops, paralyzing our cities, hobbling our economies, "terrorizing" us, in every sense of the word.
The enemy is bloodyminded, sophisticated, ruthless, rich, and fatalistic. Every attack---every message---is a political as well as terrorist event: to demonstrate power, confidence, fearlessness, and reach.
Remember the note, left by one of the Madrid bombers after that 2004 attack? It said, "You choose life. WE choose death." Well, yes, we DO choose life. And our WAY of life. And as long as WE have the strength and the confidence to remember what happened six years ago today, to call the enemy what it is, stare it right in the face, and destroy it, we will prevail.