If Prussia was attacked by France and Russia at the same time, it would be as respects the conduct of the war much the same as if there were two separate wars; at the same time the unity would appear in the negotiations.
Saxony and Austria, on the contrary, as military powers in the Seven Years’ War, were to be regarded as one; what the one suffered the other felt also, partly because the theatres of war lay in the same direction for Frederick the Great, partly because Saxony had no political independence.
Numerous as were the enemies of Buonaparte in Germany in 1813, still they all stood very much in one direction in respect to him, and the theatres of war for their armies were in close connection, and reciprocally influenced each other very powerfully. If by a concentration of all his forces he had been able to overpower the main army, such a defeat would have had a decisive effect on all the parts. If he had beaten the Bohemain grand army, and marched upon Vienna by Prague, Blücher, however willing, could not have remained in Saxony, because he would have been called upon to co-operate in Bohemia, and the Crown Prince of Sweden as well would have been unwilling to remain in the Mark.
On the other hand, Austria, if carrying on war against the French on the Rhine and Italy at the same time, will always find it difficult to give a decision upon one of those theatres by means of a successful stroke on the other. Partly because Switzerland, with its mountains, forms too strong a barrier between the two theatres, and partly because the direction of the roads on each side is divergent. France, again, can much sooner decide in the one by a successful result in the other, because the direction of its forces in both converges upon Vienna, the centre of the power of the whole Austrian empire; we may add further, that a decisive blow in Italy will have more effect on the Rhine theatre than a success on the Rhine would have in Italy, because the blow from Italy strikes nearer to the centre, and that from the Rhine more upon the flank, of the Austrian dominions.
It proceeds from what we have said that the conception of separated or connected hostile power extends through all degrees of relationship, and that therefore, in each case, the first thing is to discover the influence which events in one theatre may have upon the other, according to which we may then afterwards settle how far the different forces of the enemy may be reduced into one centre of force.
There is only one exception to the principle of directing all our strength against the centre of gravity of the enemy’s power, that is, if ancillary expeditions promise extraordinary advantages, and still, in this case, it is a condition assumed, that we have such a decisive superiority as enables us to undertake such enterprises without incurring too great risk at the point which forms our great object.
When General Bulow marched into Holland in 1814, it was to be foreseen that the thirty thousand men composing his corps would not only neutralise the same number of Frenchmen, but would, besides, give the English and the Dutch an opportunity of entering the field with forces which otherwise would never have been brought into activity.
Thus, therefore, the first consideration in the combination of a plan for a war, is to determine the centres of gravity of the enemy’s power, and, if possible, to reduce them to one. The second is to unite the forces which are to be employed against the centre of force into one great action.
Here now the following grounds for dividing our forces may present themselves:
1. The original position of the military forces, therefore also the situation of the States engaged in the offensive.