The German system of visual communication between ground troops and aircraft
is well developed. Extracts from a German document explaining the system are
reprinted below. It must he remembered, however, that the Germans take the
precaution of changing their signals as often as possible. Perhaps the chief
value of these extracts is that they illustrate basic methods of air-ground
visual signaling and the importance attached to them by the Germans.
Coordination between Army and Air Force is to be arranged through the respective
headquarters prior to each action. The appropriate headquarters of these two
branches of the service are also responsible for keeping themselves mutually
and speedily informed regarding all movements in their battle area, both on the
ground and in the air.
To speed up recognition, ground troops should possess detailed knowledge of our
own aircraft types, of the prearranged signals, and of the air situation. This
information should be distributed down to companies, whose commanders may give
orders to signal. If air crews are aware of the situation on the ground, of the
general conduct of ground troops in battle, and of the prearranged signals, gunners
will be able to distinguish more quickly between enemy troops and friendly troops.
Ground troops must give their signals early and in a position easily observed from
the air. Aircraft must be able to see the signals before arriving over the position.
Aircraft must not give their signals too soon, inasmuch as cover often interferes
with observation by ground troops. Only when the ground is flat, and when the
aircraft are flying low, may early signals be given. Since recognition by ground
troops is difficult when planes appear overhead too suddenly, unnecessarily low
flying over our own troops is to be avoided.
3. DAY SIGNALS USED BY GROUND TROOPS
In the daytime, ground troops must give recognition signals when air units call for
them by giving their own recognition signals, or if friendly aircraft threaten to attack.
Also, ground troops may give daytime recognition signals without being called upon to do
so if they consider it necessary to identify themselves to friendly aircraft—especially
where terrain features tend to obscure ground troops from air observation.
a. Orange Smoke
Orange-colored smoke is the signal most easily recognized from the air. It
means, "own troops are here." It is the chief recognition signal for all ground troops.
b. Identification Panels
Identification panels will be laid out so that they may be read from aircraft flying
toward the front. They must be arranged in good time, and on a background against which
they can be picked out clearly from the air, so that the aircraft will not be obliged to
circle over the battle area.
The panels should be spread on open ground, wherever possible, since aircraft usually
observe while approaching, and not when directly over a position. Trees, bushes, and
other objects may prevent aircraft from seeing the signals obliquely. Every effort must
be made to make the signals as large as possible. Panels may be lifted only when the
aircraft are out of sight.
Yellow cloths mean "here is our own front line." They are to be used only for this
message, so that the front line will always be clearly indicated. The aircraft can draw
its own conclusions as to the battle situation. In general, yellow is easily recognizable
from a moderate height; a number of yellow cloths spread out side by side will make
identification easier. When our own troops advance, the yellow cloths must not be left behind.
In addition, the orange smoke signal is to be used as extensively as possible.
c. Swastika Flags
Swastika flags can scarcely be identified at all from great heights, and only with
difficulty from moderate heights. They mean "own troops are here." As a rule, they
are used in rear positions, but may be used in the front line if yellow cloths are
not available or if no particular value is attached to a distinct recognition of
the front line as such. Since swastika flags alone are generally not sufficient
for identification purposes, it is advisable to use the additional signal of orange smoke.
d. Improvised Signals
If the usual recognition signals are not available, troops may improvise signals, such
as the waving of steel helmets, handkerchiefs, and so on. However, these signals afford
no guarantee that the ground troops will be recognized.
4. DAY SIGNALS USED BY AIRCRAFT
In the daytime, aircraft must give recognition signals when fired on by friendly
troops. Daytime signals may also be given by aircraft which suddenly emerge from
clouds over friendly territory, or which wish to request signals from ground troops.
Ground troops will generally identify friendly aircraft by noting the type of
plane, the national marking, or special painting. When security permits, messages
will be dropped in message boxes which emit a yellow smoke while dropping and after
reaching the ground. If these boxes are not available, messages will be dropped in
message bags, to which a red-and-white streamer is attached. Aircraft may improvise
such signals as the dipping up and down of the nose and tail of a plane, wing
dipping, or repeated spurts of the motor ("jackrabbiting").
5. NIGHT SIGNALS USED BY GROUND TROOPS
At night, ground troops must give recognition signals when these are requested by our
own aircraft, and when the situation warrants anticipating a bombing attack by our
own aircraft. Ground troops use light signals of all types, making extensive use of
Very lights. Codes are changed continually, of course, and are made known down to companies.
6. NIGHT SIGNALS USED BY AIRCRAFT
Aircraft must give night signals when there is danger of attack by friendly troops. Further,
aircraft are permitted to signal at night if they have lost their bearings and wish to know
whether they are flying over friendly territory; if they know, or believe, that they are
crossing the front on a return flight; when they wish to request friendly troops to give
signals; and when they are about to land at an airdrome. Aircraft must continually change
the meanings of their fixed light signals and flashed searchlight signals.
7. USE OF VERY LIGHTS
The Germans use white, green, and red Very lights. At the time the above instructions
were published, German aircraft used white Very lights to request ground troops to give
recognition signals: green, when a plane was about to drop a message and wished ground
troops to indicate where they preferred to have it dropped; and red, to convey the
message "Beware of enemy antitank weapons." Red smoke signals also were used to convey
this last message, while blue or violet smoke signals were used to indicate the presence
of enemy tanks.