Such was the disposition of the two armies when at half-past seven the sun pierced the mist and the first cannon-shots were exchanged. Marlborough and Eugene had decided that they would begin by pressing, as hard as might be, the assault upon the forest of Sars. When this assault should have proceeded for half an hour, the opposite end of the line, the left, under the Prince of Orange,[13] should engage the French troops holding the wood of Lanière. It was expected that the forest of Sars would be forced early in the action; that the troops in the wood of Lanière would at least be held fast by the attack of the Prince of Orange, and that the weakened French centre could then be taken by assault with the use of the reserves, of Orkney's men, and of detachments drawn from the two great masses upon the wings.
The reader may here pause to consider the excellence of this plan--very probably Marlborough's own, and one the comparative ill-success of which was due to the unexpected power of resistance displayed by the French infantry upon that day.
It was wise to put the greater part of the force into a double attack upon the forest of Sars, for this forest, with its thick woods and heavy entrenchments, was at once the strongest part of the French position in its garnishing and artificial enforcement, yet weak in that the salient angle it presented was one that could not, from the thickness of the trees, be watched from any central point, as can the salient angle of a fortification. Lottum on the one side, Schulemberg on the other, were attacking forces numerically weaker than their own, and separate fronts which could not support each other under the pressure of the attack.
It was wise to engage the forces upon the French side opposite the allied left in the wood of Lanière half an hour after the assault had begun upon the forest of Sars, for it was legitimate to expect that at the end of that half hour the pressure upon the forest of Sars would begin to be felt by the French, and that they would call for troops from the right unless the right were very busily occupied at that moment.
Finally, it was wise not to burden the centre with any great body of troops until one of the two flanks should be pressed or broken, for the centre might, in this case, be compared to a funnel in which too great a body of troops would be caught at a disadvantage against the strong entrenchments which closed the mouth of the funnel. An historical discussion has arisen upon the true rôle of the left in this plan. The commander of the allies gave it out _after_ the action (as we have seen above) that the left had only been intended to "feint." The better conclusion is that they were intended to do their worst against the wood of Lanière, although of course this "worst" could not be expected to compare with the fundamental attack upon the forest of Sars, where all the chief forces of the battle were concentrated.