This was completely the effect of a surprise, for if Bluecher had thought of such a near possibility of an attack from Buonaparte( *) he would have organised his march quite differently.

To this mistake of Bluecher's the result is to be attributed.

Buonaparte did not know all these circumstances, and so there was a piece of good fortune that mixed itself up in his favour.
(*) Bluecher believed his march to be covered by Pahlen's Cossacks, but these had been withdrawn without warning to him by the Grand Army Headquarters under Schwartzenberg.
It is the same with the battle of Liegnitz, 1760.

Frederick the Great gained this fine victory through altering during the night a position which he had just before taken up.

Laudon was through this completely surprised, and lost 70 pieces of artillery and 10,000 men.