But he was now no match for Napoleon.

To stay meant annihilation.

He hastily made his disposition for a rear guard defense and a withdrawal.

He made a stubborn rear guard battle of it during the day, and, although he lost heavily in men, guns and supplies, he finally succeeded in crossing the Marne and breaking the bridges behind him.
Macdonald had moved tardily.

If he had shown half the enterprise of the Emperor he would have been at the crossing of the Marne in good time and Yorck would have been caught in a trap whence he could not have extricated himself.