When we come to study the details of the story, we shall see that this, the Prussian defeat at Ligny, was thus incomplete because one of Napoleon's subordinates, Erlon, with the First French Army Corps, received contradictory orders and did not come up as he should have done to turn the battle of Ligny into a decisive victory for Napoleon. A part of Napoleon's forces being thus neutralised and held useless during the fight at Ligny, the Prussian army escaped, still formed as a fighting force, and still capable of reappearing, as it did reappear, at the critical moment, two days later, upon the field of Waterloo. THE ADVANCE The rapidity of Napoleon's stroke was marred at its very outset by certain misfortunes as well as certain miscalculations. His left, which was composed of the First and Second Corps d'Armée, did indeed reach the river Sambre in the morning, and had carried the bridge of Marchiennes by noon, but the First Corps, under Erlon, were not across--that is, the whole left had not negotiated the river--until nearly five o'clock in the afternoon. Next, the general in command of the leading division of the right-hand body--the Fourth Corps--gave the first example of that of which the whole Napoleonic organisation was then in such terror, I mean the mistrust in the fortunes of the Emperor, and the tendency to revert to the old social conditions, which for a moment the Bourbons had brought back, and which so soon they might bring back again--he deserted. The order was thereupon given for the Fourth Corps or right wing to cross at Châtelet, but it came late (as late as half-past three in the afternoon), and did but cause delay. At this eastern end of Napoleon's front the last men were not over the river until the next day.