Nor was there any supporting infantry.

Indeed, the retreat of the Prussians had been so sudden and so rapid that Grouchy's horse had been hard put to it to intercept them.
The regiments leading the allied retreat were formed in squares, and with musketry and cannon animated with the courage of despair, they forced a passage through the charging, barring masses of the French cavalry, not, however, without losing several of the squares in the process.

It was their only possible way to safety.

As it was, Bluecher himself narrowly escaped capture.
Napoleon's soldiers had fought five pitched battles in four days.

As a preparation, they had marched thirty miles, night and day, over incredible roads.