It was by a neglect of this principle that Frederick was beaten at
Kollin in the first campaign of 1757. Notwithstanding prodigies of
valor, the Prussians lost fifteen thousand men and a great portion of
their artillery, while the loss of the Austrians did not exceed five
thousand men. The consequence of this battle was more unfortunate
still, since it obliged the King of Prussia to raise the siege of
Prague, and to evacuate Bohemia.
It was also by making a flank march before the Prussian army, that the
French lost the disgraceful battle of Rosbach.
This imprudent movement was still more to be reprehended, because the
Prince de Soubise, who commanded the French army, was so negligent as
to manœuvre, without either advanced guards or flanking corps, in
presence of the enemy. The result was, that his army, consisting of
fifty thousand men, was beaten by six battalions and thirty squadrons.
The French lost seven thousand men, twenty-seven standards, and a great
number of cannon. The Prussians had only three hundred men disabled.
Thus, by having forgotten this principle, _that a flank march is never
to be made before an enemy in line of battle_, Frederick lost his army
at Kollin; and Soubise, at Rosbach, lost both his army and his honor.