tified places should be in echelon, on three lines, and
should extend from the frontiers toward the capital.[20] There should be
three in the first line, as many in the second, and a large place in the
third, near the center of the state. If there be four fronts, this would
require, for a complete system, from twenty-four to thirty places.

It will be objected that this number is large, and that even Austria has
not so many. It must be recollected that France has more than forty upon
only a third of its frontiers, (from Besancon to Dunkirk,) and still has
not enough on the third line in the center of the country. A Board
convened for the purpose of considering the system of fortresses has
decided quite recently that more were required. This does not prove that
there were not already too many, but that certain points in addition
should be fortified, while those on the first line, although too much
crowded, may be maintained since they are already in existence.
Admitting that France has two fronts from Dunkirk to Basel, one from
Basel to Savoy, one from Savoy to Nice, in addition to the totally
distinct line of the Pyrenees and the coast-line, there are six fronts,
requiring forty to fifty places. Every military man will admit that this
is enough, since the Swiss and coast fronts require fewer than the
northeast. The system of arrangement of these fortresses is an important
element of their usefulness. Austria has a less number, because she is
bordered by the small German states, which, instead of being hostile,
place their own forts at her disposal. Moreover, the number above given
is what was considered necessary for a state having four fronts of
nearly equal development. Prussia, being long and narrow, and extending
from Koenigsberg almost to the gates of Metz, should not be fortified
upon the same system as France, Spain, or Austria. Thus the geographical
position and extent of states may either diminish or increase the number
of fortresses, particularly when maritime forts are to be included.

2. Fortresses should always occupy the important strategic points
already designated in Article XIX. As to their tactical qualities, their
sites should not be commanded, and egress from them should be easy, in
order to increase the difficulty of blockading them.

3. Those which possess the greatest advantages, either as to their own
defense or for seconding the operations of an army, are certainly those
situated on great river