One thing, at any rate, is quite clear, and that is that neither of the allied commanders acted, so far as we can judge, in pursuance of any such agreement. Blücher, when he hears of Napoleon’s advance to Charleroi, orders his army to assemble at Sombreffe, and then sends word to Wellington of what he has done; the latter, as we have seen, although he learns that the enemy’s main attack is by way of Charleroi and therefore upon the Prussians, and although he has long known that in this event it was Blücher’s intention to concentrate his army at Sombreffe, takes no instant steps to bring his army into close union with that of Blücher. His first idea, certainly, is to assemble his army at Nivelles. This difficulty, it is true, does not seem greatly to trouble the writers who have adopted the theory of a previous understanding or arrangement; it seems to be possible, for instance, for Siborne, to believe that Wellington had agreed to concentrate at Quatre Bras,[197] and yet actually to call attention[198] to the fact that he halted Picton’s division at Waterloo, hours after he had known that Blücher was concentrating at Sombreffe, because he had not then made up his mind whether to send Picton to Nivelles or to Quatre Bras. But he and those other historians who have followed him, or have adopted the same theory, have certainly a serious difficulty to contend with. The Duke had been informed about mid-night[199] that Quatre Bras was occupied by a part of Perponcher’s division, and he had heard also that Blücher was concentrating his army at Sombreffe. If he had agreed with Blücher to concentrate the Anglo-Dutch army at Quatre Bras, he would assuredly have given his orders accordingly, and in season,—at least one would suppose so,—and he certainly could have had a large force there by ten o’clock in the morning. But he acted, on the other hand, as if he thought that he possessed perfect discretion as to what he would do,—as if he was bound by no agreement whatsoever. It is evident, in fact, that he did not make up his mind till shortly before he left Brussels to go to Quatre Bras himself, whether he would undertake to hold the place or not.