President George Bush once put forth, "Using military force makes sense as a policy where the stakes warrant, where and when force can be effective, where its application can be limited in scope and time, and where the potential benefits justify the potential costs and sacrifice." (President George Bush, p.423) This criterion as Bush describes is nothing new. It has been traditionally known as international law. They are also part of what is known as just war theory. Some people have preferred the use of the phrase "justified war" instead of "just war" because they believe that in just war theory there is a presumption against the use of military force that must be overcome or should it? .
Just war theory can be traced all the way back to 400 A.D. by the writings of St. Augustine. He was concerned about how to reconcile traditional Christian views of the immorality of violence with the necessity of defending the Roman Empire from invading forces. He asked "what one should do if one sees an individual attacking an innocent, defenseless victim? His response was that "one should intervene and do whatever is necessary to protect the victim, even up to the point of killing the aggressor." (St. Augustine, p. 424) We know of this theory today by The Hague and Geneva conventions. .
Remember, also that human beings have been fighting each other since prehistoric times. But is war really bad? The ethics of war starts by assuming that yes, war is bad, and it should be avoided whenever possible, but it recognizes that there can be situations when war may be lesser evil of several bad choices. War itself is bad but when justified it serves a purpose to protect the life of human individuals. Although war itself can be backed by a number of ethical theories, ethical egoism sort of stands back and says, yeah if I was in charge on the United States, of course I am going to act the way I ought to act in order to save the already harmed and also save the innocent lives of people from dying.