For a long period previous to the Thirty Years' War, its strong castles
and fortified cities secured the German empire from attacks from abroad,
except on its extensive frontier, which was frequently assailed, but no
enemy was able to penetrate to the interior till a want of union among
its own princes opened its strongholds to the Swedish conqueror; nor
then, did the cautious Gustavus Adolphus venture far into its
territories till he had obtained possession of all the military works
that might endanger his retreat.

Again, in the Seven Years' War, when the French neglected to secure
their foothold in Germany, by placing in a state of defence the
fortifications that fell into their power, the first defeat rendered
their ground untenable, and threw them from the Elbe back upon the Rhine
and the Mayne. They afterwards took the precaution to fortify their
positions, and to secure their magazines under shelter of strong places,
and, consequently, were enabled to maintain themselves in the hostile
country till the end of the war, notwithstanding the inefficiency of
their generals, the great reverses they sustained in the field, the
skill and perseverance of the enemy they were contending with, and the
weak and vacillating character of the cabinet that directed them.

But this system of defence was not so carefully maintained in the latter
part of the eighteenth century, for at the beginning of the French
Revolution, says Jomini, "Germany had too few fortifications; they were
generally of a poor character, and improperly located." France, on the
contrary, was well fortified: and although without armies, and torn in
pieces by domestic factions, (we here use the language of the Archduke,)
"she sustained herself against all Europe; _and this was because her
government, since the reign of Louis XIII_., _had continually labored to
put her frontiers into a defensive condition agreeably to the principles