t actual aerial combat usually
engaged only two or four aviators.

Early in February of the second year of the war, several famous French
aviators fell victims to the new mode of warfare. It seems that as
soon as a machine would appear above the trenches in that section, six
or more German machines would rise quickly and surround the Frenchman.
Outnumbered and surrounded on all sides the French machines rarely got
back safely to their lines, among the first to be lost being George
Boillot, world-famous as an automobile racer.

The German tactics at once were imitated and improved on by the allied
forces, and by July, 1916, the French had perfected a system of
defense which, paradoxically speaking, may be termed "air-tight."
French aviation squadrons would be held in readiness at all times to
repel attacks, and twenty machines usually were considered a "unit."
At first sign of a hostile aeroplane approaching, ten French machines
would rise at top speed to a height of 10,000 feet, while five minutes
later the second ten would follow, rising to 5,000 feet. The
attacking machine usually would be found at a height intermediate
between the upper and lower French squadrons, both of which would
attack the invader vigorously, and with highly satisfactory results.

One of the lessons of these true aerial battles between opposing
squadrons has been the efficiency of the biplane, as compared with
that of the monoplane. When the war started the monoplane was
considered the machine par excellence for war use; its high speed and
quick maneuvering being cited as most important for fighting in the
air. Eighteen months of aerial battles have shown that for all-round
fighting, bombing and reconnoitering the biplane is far more
effective, and the construction of new monoplanes has been practically
abandoned by the allied governments. The Germans, it is true, have
found the Fokker type of monoplane a very efficient one, but the
number of Fokkers in use is comparatively small, when the great fleets
of Aviatiks and other well-known types of German biplanes are
remembered.

Exact statistics regarding the number of aeroplanes at present in use
along the various battle fronts are not available, but estimates made
by aviation officers, by correspondents and from notes in the
respective publications devoted to aviation abroad, fix it as in
excess of 12,000 machines. More than half of these are used by the
Allies on the western front; Germany