The first when he left Dresden so suddenly in July 1760, and falling upon Lascy, then turned against Dresden, gained nothing by the whole of that intermezzo, but rather placed his affairs in a condition notably worse, as the fortress Glatz fell in the meantime.
In 1813, Buonaparte turned suddenly from Dresden twice against Bluecher, to say nothing of his incursion into Bohemia from Upper Lusatia, and both times without in the least attaining his object.

They were blows in the air which only cost him time and force, and might have placed him in a dangerous position in Dresden.
Therefore, even in this field, a surprise does not necessarily meet with great success through the mere activity, energy, and resolution of the Commander; it must be favoured by other circumstances.

But we by no means deny that there can be success; we only connect with it a necessity of favourable circumstances, which, certainly do not occur very frequently, and which the Commander can seldom bring about himself.
Just those two Generals afford each a striking illustration of this.

We take first Buonaparte in his famous enterprise against Bluecher's Army in February 1814, when it was separated from the Grand Army, and descending the Marne.

It would not be easy to find a two days' march to surprise the enemy productive of greater results than this; Bluecher's Army, extended over a distance of three days' march, was beaten in detail, and suffered a loss nearly equal to that of defeat in a great battle.