It is plain that whatever happens wars are fought to effect a psychological change in the antagonist. They are then fought for a psychological end unless they are wars of extermination. These are rare. The United States could not find a people on the face of the earth whose ideas and language were unknown to all Americans. Where there is a chance of communication, there is always the probability that one of the antagonistic organizations (governments)--which have already cooperated to the extent of meeting one another's wishes to fight--will subsequently cooperate on terms of primary advantage to the victors. Since the organizations comprise human beings with human ways of doing things, the change must take place in the minds of those specific individuals who operate the existing government, or in the minds of enough other people for that government to be overthrown. The fact that war is waged against the minds, not the bodies, of the enemy is attested by the comments of military writers of all periods. The dictum of Carl von Clausewitz that "war is politics continued by other means" is simply the modern expression of a truth recognized since antiquity. War is a kind of persuasion--uneconomical, dangerous, and unpleasant, but effective when all else fails. =Ideology.= An ideology is a system of deep-rooted beliefs about fundamental questions in human life and affairs.[11] Ideology also plays a part in psychological warfare. A difference in beliefs which does not touch fundamentals is commonly termed a difference of _opinion_. You may believe in high tariffs; and I, in no tariff. You may believe in One World; I may not. You may support Republicans; I, Democrats. Despite these differences both of us can still believe in dollars as a method of paying income, in marriage as a system of setting up the family, in private property for most goods industrial or personal, in the Government of the United States, in majority rule, in democratic elections, in free speech, and so on. If our difference of opinion is so inclusive that we can agree on nothing political, our differences have gone from mere opinion into the depths of _ideology_. Here the institutional framework is affected. You and I would not want to live in the same city; we could not feel safe in one another's presence; each would be afraid of the effect which the other might have on the morals of the community. If I were a Nazi, and you a democrat, you would not like the idea of my children living next door to yours. If I believed that you were a good enough creature--poor deluded devil--but that you were not fit to vote, scarcely to be trusted with property, not to be trusted as an army officer, and generally subversive and dangerous, you would find it hard to get along with me.