It is rarely, however, that a single battle between armies has decided the issue of a war. The campaigns of Jena and Sadowa are indeed instances in point. But they are in their way as exceptional as is the Boer War--decided without a pitched battle being fought at all. These may be regarded as the extremes. Normally, war may end victoriously for one side without the other having been deprived of the means of continuing even effective resistance. In such cases it is some moderation in the victor’s terms, some change in the ambition of the partially defeated side, or, at least, a sense that no adequate results can be expected from further fighting, that has brought about the cessation of hostilities. But, again, there are wars in which the issues can admit of no compromise at all. The invasions of Tamerlane, Attila, and the Mohammedan conquerors were not wars but campaigns of extermination. It is in such a war that we are engaged to-day. The stake for every country is of a vital character, so that compromise is indistinguishable from defeat, and defeat must carry with it the negation of everything which makes national life tolerable. The Germans have convinced themselves that there is no alternative to world dominion but downfall, and the civilized world is determined that there shall be no German world dominion. Such a struggle by its nature permits of no end by arrangement or negotiation. It must go forward until either one side or the other is either militarily defeated or until the economic strain disintegrates the state. In such conditions a secondary form of military pressure may be of paramount importance. Now if we go back to our first definition of war, as a struggle in which the opposing sides pit their armed forces against each other and abide by the issue of the combat, we must remember that, just as it is rare for a war to be decided by a single combat, so is it rare for a single combat to dissipate and destroy an army. Ordinary prudence dictates that there shall be protected lines or some strong place into which it can retreat in the event of defeat. And when it is thus compelled to abandon open fighting and seek a position of natural or artificial strength, it becomes the business of the stronger to complete the business by destroying and penetrating the defences. But if this is too costly a proceeding, the stronger tries to contain the force so protected and passes on, if possible, to investment and siege. The simplest case of this is the complete encirclement and siege of the great city or camp, of which the war of 1870 gave two such striking examples in Metz and Paris.