territorial perceptiveness which aeronautical surveys make
possible to a general of to-day. While war has not changed, it is
true that a commander of an army in modern campaign is compelled
to review and to take into account a far larger group of factors. A
modern general must be capable of grasping increased complexities,
and must possess a synthetic mind to be able to reduce all these
complicating factors into a single whole. The first factor of the
battles of the Marne was the topographical factor, the consideration
of the land over which the action was to take place.

Let the River Marne be used as a base from which this topography can
be determined. The Marne rises near Langres, which is the northwest
angle of that pentagon of fortresses (Belfort, Epinal, Langres, Dijon,
and Besancon), which incloses an almost impregnable recuperative
ground for exhausted armies. From Langres the Marne flows almost north
by west for about fifty miles through a hilly and wooded country,
then, taking a more westerly course, it flows for approximately
seventy-five miles almost northwest, across the Plain of Champagne,
past Vitry-le-Francois and Chalons, thence almost due westward
through the Plateau of Sezanne, by Epernay, Chateau Thierry, La
Ferte-sous-Jouarre, and Meaux to join the Seine just south of Paris.
In the neighborhood of Meaux, three small tributaries flow into
the Marne--the Ourcq from the north, and the Grand Morin and Petit
Morin from the east. The Marshes of St. Gond, ten miles long from
east to west and a couple of miles across, lie toward the eastern
borders of the Plateau of Sezanne, and form the source of the Petit
Morin, which has been deepened in the reclamation of the marsh
country.

Once more considering the source of the Marne, near Langres, it
will be noted that the River Meuse rises near by, flowing north
by east to Toul, and then north-northwest past Verdun to Sedan,
where it turns due north, flowing through the Ardennes country
to Namur, in Belgium. To the east of the Meuse lies the difficult
forest clad hill barrier, known as the Hills of the Meuse; to the
east extends (as far as Triaucourt) the craggy and broken wooded
country of the Argonne, a natural barrier which stretches southward
in a chain of lakes and forests.

West of this impassible country of the Meuse and the Argonne lies
the plain of Champagne-Pouilleuse, which is almost a steppe, bare
and open, only slightly undulating, overgrown with