The war on terror is a war fought in the <em>mind. </em>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 <em>never </em>end, as the war's main "general" is in the mind, and you cannot wage war on the thoughts of individuals.
The answer to that is C. sending Romans overseas as soldiers left fewer farmers near Rome and led to severe food shortages.