II
THE PRELIMINARIES: NAPOLEON’S ADVANCE ACROSS THE SAMBRE
To understand the battle of Waterloo it is necessary, more perhaps than in the case of any other great decisive action, to read it strategically: that is, to regard the final struggle of Sunday the 18th of June as only the climax of certain general movements, the first phase of which was the concentration of the French Army of the North, and the second the passage of the Sambre river and the attack. This second phase covered four days in time, and in space an advance of nearly forty miles.
There is a sense, of course, in which it is true of every battle that its result is closely connected with the strategy which led up to its tactical features: how the opposing forces arrived upon the field, in what condition, and in what disposition and at what time, with what advantage or disadvantage, is always necessarily connected with the history of the campaign rather than of the individual action; but, as we saw in the case of Blenheim, and as might be exemplified from a hundred other cases, the greater part of battles can be understood by following the tactical dispositions upon the field. They are won or lost, in the main, according to those dispositions.
With Waterloo it was not so. Waterloo was lost by Napoleon, won by the Allies, not mainly on account of tactical movements upon the field itself, but mainly on account of what had happened in the course of the advance of the French army to that field. In other words, the military character of that great decisive action is always missed by those who have read it isolated from the movements immediately preceding it.
Napoleon, determining to strike at Belgium under the political circumstances we have already seen, was attacking forces about double his own.
He was like one man coming up rapidly and almost unexpectedly to attack two: but hoping if possible to deal successively and singly with either opponent.
His doubtful chance of success in such a hazard obviously lay in his being able to attack each enemy separately: that is, to engage first one before the second came to his aid; then the second; and thus to defeat each in turn. The chance of victory under such circumstances is slight. It presupposes the surprise of the two allied adversaries by their single opponent, and the defeat of one so quickly that the other cannot come to his aid till all is over. But no other avenue of victory is open to a man fighting enemies of double his numerical strength; at least under conditions where armament, material, and racial type are much the same upon either side.
The possibility of dealing thus with his enemy Napoleon thought possible, and thought it possible from two factors in the situation before him.
The first factor was that the allied army, seeing its great numbers, the comparatively small accumulation of supplies which it could yet command, the great length of frontier which it had to watch, was spread out in a great number of cantonments, the whole stretch of which was no less than one hundred miles in length, from Liège upon the east or left to Tournay upon the west or right.