An acrimonious discussion has arisen as to whether he promised to come up and help Blucher shortly afterwards or not, but it is a discussion beside the mark, for, in the first place, Wellington quite certainly _intended_ to come up and help the Prussians; and in the second place, he was quite as certainly _unable_ to do so, for the French opposition under Ney which he had under-estimated, turned out to be a serious thing. But his letter, and his undoubted intention to come up and help Blucher, depended upon his belief that the units of his army were all fairly close, and that by, say, half-past one he would have the whole lot occupying the heights of Quatre Bras. Now, as a fact, the units of Wellington's command were scattered all over the place, and it is astonishing to note the discrepancy between his idea of their position and their real position on the morning of the day when Quatre Bras was fought. When one appreciates what that discrepancy was, one has a measure of the bad staff work that was being done under Wellington at the moment. [Illustration] The plan (p. 127)[12] distinguishes between the real positions of Wellington's command on the morning of the 16th when he was writing his letter to Blucher and the positions which Wellington, in that letter, erroneously ascribes to them. It will show the reader the wide difference there was between Wellington's idea of where his troops were and their actual position on that morning. It needs no comment. It is sufficient in itself to explain why the action at Quatre Bras consisted not in a set army meeting and repelling the French (it could have destroyed them as things turned out, seeing Erlon's absence), but in the perpetual arrival of separate and hurried units, which went on from midday almost until nightfall. IV THE ALLIED RETREAT AND FRENCH ADVANCE UPON WATERLOO AND WAVRE When the Prussians had concentrated to meet Napoleon at Ligny they had managed to collect, in time for the battle, three out of their four army corps. These three army corps were the First, the Second, and the Third, and, as we have just seen, they were defeated. But, as we have also seen, they were not thoroughly defeated. They were not disorganised, still less were the bulk of them captured and disarmed. Most important of all, they were free to retreat by any road that did not bring them against their victorious enemy. In other words, they were free to retreat to the north as well as to the east.