The war on terror is a war fought in the mind. Terrorist ideologies are held in the minds of individuals willing to carry out attacks on any given target with the intent of spreading fear and a message. The war in Vietnam may have been to combat communism, but we left after a certain while. We weren't contentiously attacked by Viet Cong after pulling out of the area, like we are by terrorists. The war on terror is a war that will never end, as the war's main "general" is in the mind, and you cannot wage war on the thoughts of individuals.