The second phase was a very different matter. It developed into what were essentially two battles. It found Napoleon fighting not only against Wellington in front of him, but against Blucher to his right and almost behind him. It was no longer a simple business of hammering with the whole force of the French army at the British and their allies upon the ridge in front, but of desperately attempting to break the Anglo-Dutch line against time, with diminishing and perpetually reduced forces; with forces perpetually reduced by the necessity of sending more and more men off to the right to resist, if it were possible, the increasing pressure of the accumulating Prussian forces upon the right flank of the French. This second phase of the action at Waterloo began in the neighbourhood of four o'clock. It is true that the arriving Prussians had not yet debouched from the screen of wood that hid them two and a half miles away to the east, but at that hour (four o'clock) the heads of their columns were all ready to debouch, and the delay between their actual appearance upon the field and the beginning of the second half of the battle was not material to the result. That second half of the action began with a series of great cavalry charges which the Emperor had not designed, and which, even as he watched them, he believed would be fatal to him. As spectacles, these famous rides presented the most awful and memorable pageant in the history of modern war; as tactics they were erroneous, and grievously erroneous. Before this second phase of the battle was entered it was easily open to Napoleon, recognising the Prussians advancing and catching no sight of Grouchy, to change his plan, to abandon the offensive, to stand upon the defensive along the height which he commanded, there to await Grouchy, and, if Grouchy still delayed, to maintain the chances of an issue which might at least be negative, if he could prevent its being decisively disastrous. But even if such a conception had passed through the Emperor's mind, military science was against it. If ever those opposed to him had full time to concentrate their forces he would, even with the reinforcement of Grouchy, be fighting very nearly two to one. His obvious, one might say his necessary, plan was to break Wellington's line, if still it could be broken, before the full pressure of the arriving Prussians should be felt. Short of that, there could be nothing but immediate or ultimate disaster. We shall see how, much later in the action, yet another opportunity for breaking away, and for standing upon the defensive, or for retreating, was, in the opinion of some critics, offered to the Emperor by fate. But we shall see how, upon that second and later occasion in the day, his advantage in so doing was even less than it was now between this hour of half-past three and four o'clock, when he determined to renew the combat.