On War

by Carl von Clausewitz

If the concentration of the forces would occasion detours and loss of time, and the danger of advancing by separate lines is not too great, then the same may be justifiable on those grounds; for to effect an unnecessary concentration of forces, with great loss of time, by which the freshness and rapidity of the first blow is diminished, would be contrary to the second leading principle we have laid down. In all cases in which there is a hope of surprising the enemy in some measure, this deserves particular attention.

But the case becomes still more important if the attack is undertaken by allied States which are not situated on a line directed towards the State attacked not one behind the other but situated side by side. If Prussia and Austria undertook a war against France, it would be a very erroneous measure, a squandering of time and force if the armies of the two powers were obliged to set out from the same point, as the natural line for an army operating from Prussia against the heart of France is from the Lower Rhine, and that of the Austrians is from the Upper Rhine. Concentration, therefore, in this case, could only be effected by a sacrifice; consequently in any particular instance, the question to be decided would be, Is the necessity for concentration so great that this sacrifice must be made?

2. The attack by separate lines may offer greater results.

As we are now speaking of advancing by separate lines against one centre of force, we are, therefore, supposing an advance by converging lines. A separate advance on parallel or eccentric lines belongs to the rubric of accessory undertakings, of which we have already spoken.

Now, every convergent attack in strategy, as well as in tactics, holds out the prospect of great results; for if it succeeds, the consequence is not simply a defeat, but more or less the cutting off of the enemy. The concentric attack is, therefore, always that which may lead to the greatest results; but on account of the separation of the parts of the force, and the enlargement of the theatre of war, it involves also the most risk; it is the same here as with attack and defence, the weaker form holds out the greater results in prospect.

The question, therefore, is, whether the assailant feels strong enough to try for this great result.

When Frederick the Great advanced upon Bohemia, in the year 1757, he set out from Saxony and Silesia with his forces divided. The two principal reasons for his doing so were, first, that his forces were so cantoned in the winter that a concentration of them at one point would have divested the attack of all the advantages of a surprise; and next, that by this concentric advance, each of the two Austrian theatres of war was threatened in the flanks and the rear. The danger to which Frederick the Great exposed himself on that occasion was that one of his two armies might have been completely defeated by superior forces; should the Austrians not see this, then they would have to give battle with their centre only, or run the risk of being thrown off their line of communication, either on one side or the other, and meeting with a catastrophe; this was the great result which the king hoped for by this advance. The Austrians preferred the battle in the centre, but Prague, where they took up their position, was in a situation too much under the influence of the convergent attack, which, as they remained perfectly passive in their position, had time to develop its efficacy to the utmost. The consequence of this was that when they lost the battle, it was a complete catastrophe; as is manifest from the fact that two-thirds of the army with the commander-in-chief were obliged to shut themselves up in Prague.

This brilliant success at the opening of the campaign was attained by the bold stroke with a concentric attack. If Frederick considered the precision of his own movements, the energy of his generals, the moral superiority of his troops, on the one side, and the sluggishness of the Austrians on the other, as sufficient to ensure the success of his plan, who can blame him? But as we cannot leave these moral advantages out of consideration, neither can we ascribe the success solely to the mere geometrical form of the attack. Let us only think of the not less brilliant campaign of Buonaparte’s, in the year 1796, when the Austrians were so severely punished for their concentric march into Italy. The means which the French general had at command on that occasion, the Austrian general had also at his disposal in 1757 (with the exception of the moral), indeed, he had rather more, for he was not, like Buonaparte, weaker than his adversary. Therefore, when it is to be apprehended that the advance on separate converging lines may afford the enemy the means of counteracting the inequality of numerical forces by using interior lines, such a form of attack is not advisable; and if on account of the situation of the belligerents, it must be resorted to, it can only be regarded as a necessary evil.

If, from this point of view, we cast our eyes on the plan which was adopted for the invasion of France in 1814, it is impossible to give it approval. The Russian, Austrian, and Prussian armies were concentrated at a point near Frankfort on the Maine, on the most natural and most direct line to the centre of the force of the French monarchy. These armies were then separated, that one might penetrate into France from Mayence, the other from Switzerland. As the enemy’s force was so reduced that a defence of the frontier was out of the question, the whole advantage to be expected from this concentric advance, if it succeeded, was that while Lorraine and Alsace were conquered by one army, Franche-Comte would be taken by the other. Was this trifling advantage worth the trouble of marching into Switzerland? We know very well that there were other (but just as insufficient) grounds which caused this march; but we confine ourselves here to the point which we are considering.

On the other side, Buonaparte was a man who thoroughly understood the defensive to oppose to a concentric attack, as he had already shown in his masterly campaign of 1796; and although the Allies were very considerably superior in numbers, yet the preponderance due to his superiority as a general was on all occasions acknowledged. He joined his army too late near Chalons, and looked down rather too much, generally, on his opponents, still he was very near hitting the two armies separately; and what was the state he found them in at Brienne? Blücher had only 27,000 of his 65,000 men with him, and the great army, out of 200,000, had only 100,000 present. It was impossible to make a better game for the adversary. And from the moment that active work began, no greater want was felt than that of re-union.