One can argue that terrorism has failed historically as a strategic weapon. But that's no cause for comfort. There is no doubt that it has caused great damage to American interests and those of our friends around the world. For example, terrorism has prolonged the Israeli-Palestinian conflict, and the North Ireland conflict for decades. Real progress toward peace making in these struggles has come only when terrorism has been renounced and its practitioners marginalized.
Terrorism also has a high economic cost.
Terrorism can also cripple entire economies. For example, in Egypt, by targeting a few tourists, terrorists almost shut down the vitally important tourist industry for many months. Technology has also added to the terrorist threat. In 1605, the terrorist Guy Fawkes planted 29 barrels of explosives in a plot to blow up King James and the British Parliament. Today, a small explosive device in a purse could achieve the same effect.