, and the National Guards deserted their colors and returned to
France. The only hope of the Republicans, at this crisis, was Vauban's
line of Flemish fortresses. These alone saved France. The strongholds of
Lille, Conde, Valenciennes, Quesnoy, Landrecies, &c., held the Austrians
in check till the French could raise new forces and reorganize their
army. "The important breathing-time which the sieges of these
fortresses," says an English historian, "afforded to the French, and the
immense advantage which they derived from the new levies which they
received, and fresh organization which they acquired during that
important period, is a signal proof of the vital importance of
fortresses in contributing to national defence. Napoleon has not
hesitated to ascribe to the three months thus gained the salvation of
France. It is to be constantly recollected that the Republican armies
were then totally unable to keep the field; that behind the frontier
fortresses there was neither a defensive position, nor a corps to
reinforce them; and that if driven from their vicinity, the capital was
taken and the war concluded."

In the following year, 1794, when France had completed her vast
armaments, and, in her turn, had become the invading power, the enemy
had no fortified towns to check the progress of the Republican armies;
which, based on strong works of defence, in a few weeks overran
Flanders, and drove the allies beyond the Rhine.

In the campaign of 1796, when the army of Moreau had been forced into a
precipitate retreat by the admirable strategic operations of the
Archduke Charles, the French forces owed their safety to the
fortifications on the Rhine. These works arrested the enemy's pursuit
and obliged him to resort to the tedious operations of sieges; and the
reduction of the French advanced posts alone, Kehl and Huninguen, poorly
as they were defended, employed all the resources of the Austrian army,
and the skill of their engineers, from early in October till late in
February. Kehl was at first assaulted by a force _four_ times as
numerous as the garrison; if the enemy had succeeded, he would have cut
off Moreau's retreat, and destroyed his army. Fortunately the place was
strong enough to resist all assaults; and Moreau, basing himself on the
fortresses of Alsace, his right covered by Huninguen, Neuf-Brisach, and
Befort, and his left by the iron barrier of the Netherlands, effectually
checked the waves of Austrian success.