This bitter lesson he was soon to learn. On the momentous afternoon of the twentieth, as has been related, about sixteen thousand French confronted nearly twenty-five thousand of the allies in the sharp but indecisive skirmishes before Arcis; the loss of the former was eighteen hundred, that of the allies twenty-seven hundred. In spite of the dimensions which these conflicts had assumed, Napoleon remained firm in the belief that he had to do with his retreating enemy's rear-guard; Schwarzenberg, on the other hand, was convinced that the French had a strength far beyond the reality. During the night both armies were strongly reinforced, and in the early morning Napoleon had twenty-seven thousand five hundred men--quite enough, he believed, to demoralize the retreating Austrians. It was ten o'clock when he ordered the attack, Ney and Sebastiani being directed to the plateau behind the town. What was their surprise and dismay to find Schwarzenberg's entire army, which numbered not less than a hundred thousand, drawn up in battle array on the plain to the eastward, the infantry in three dense columns, cavalry to right and left, with three hundred and seventy pieces of artillery on the central front! The spectacle would have been dazzling to any but a soldier: the bright array of gay accoutrements, the glittering bayonets, the waving banners, and the serried ranks. As it was, the audacious French skirmishers instinctively felt the incapacity of a general who could thus assemble an army as if on purpose to display its numbers and expose it to destruction. Without a thought they began a sort of challenging rencounter with horse-artillery and cavalry. But the Emperor's hopes were dashed when he learned the truth; with equal numbers he would have been exultant; a battle with odds of four to one he dared not risk. Sebastiani was kept on the heights to mask the retreat which was instantly determined upon, and at half-past one it began. This ruse was so successful, by reason of the alarms and crossings incident to the withdrawal of the French, that the allies were again terror-stricken; even the Czar rejected every suggestion of attack; again force was demoralized by genius. At last, however, scouts brought word that columns of French soldiers were debouching beyond the Aube, and the facts were plain. Even then the paralyzed invaders feared to attack, and it was not until two thirds of Napoleon's force was behind the stream that, after fierce fighting, the French rear was driven from the town. Oudinot's corps was the last to cross the river, and, standing until sappers had destroyed the bridge, it hurried away to follow the main column toward Vitry. The divisions of Gerard and Macdonald joined the march, and there were then forty-five thousand men in line.