To prove what we have said, it is only necessary to remark, that the natural bases and points of retreat of the Prussian and English armies were different; the former being directed on Maestricht, the other on Antwerp, where each expected their reinforcements. Regardless of this, and with full confidence in each other, the Prince Maréchal Blucher, and the Duke of Wellington, agreed to act in conjunction against the French army. The union of their forces, for which both were prepared, was destined to have taken place at Ligny, where the duke designed to have supported the Prussians, and where Blucher hazarded an action in expectation of his ally's assistance. The active movements of Napoleon, and the impossibility of the English force being sufficiently concentrated at Quatre-bras to afford the means of overpowering Ney and the force in their front, prevented their making a lateral march to relieve Blucher at that critical period. Otherwise, the parts of the bloody drama, as afterwards acted, would have been reversed, and the British army would have moved to support the Prussians at Ligny, as the Prussians came to the aid of the British at Waterloo.
Napoleon had the merit of disconcerting this plan for the time; but he did not, and could not, discover that the allied generals retained, after the loss of the battle of Ligny, the same purpose which they had adopted on the commencement of the campaign. He imagined, as did all around him, that Blucher must retreat on Namur, or in such a direction as would effectually accomplish a separation betwixt him and the English, as it was natural to think a defeated army should approach towards its own resources, instead of attempting further offensive operations. At all events, Napoleon was in this respect so much mistaken, as to believe that if Blucher did retire on the same line with the English, the means which the Prussian retained for co-operating with his allies were so limited, and (perhaps he might think) the spirit of the general so subdued, that Maréchal Grouchy, with 32,000 men, would be sufficient to keep the whole Prussian force in check. The maréchal was accordingly, as we have seen, despatched much too late, without any other instructions than to follow and engage the attention of the Prussians. Misled by the demonstration of Blucher, he at first took the road to Namur, and thus, without any fault on his part, lost time, which was inconceivably precious.