he advantage at first, but
B is speedier and rapidly overhauls A. During the whole period of the
overhauling movement the gun of B can be directed upon A, while the
latter, owing to the arc of training being limited to c d cannot reply.
Obviously in the running fight it would be to the advantage of B,
although the fleeter machine, to keep behind A (position 1), but the
latter is making towards its own lines.

Under these circumstances A must be headed off, so B crowds on speed
to consummate this end. But in the overtaking process B renders his
gun-fire ineffective, inasmuch as B passes beyond the arc of his gun
which is represented by e f. But in so doing B comes within the firing
arc of A (position 9). To minimise this danger B ascends to a higher
level to obtain the paramount position.

If, however, B were equipped with an astern gun the aeroplane A would
be within the fire of B when the forward gun of the latter could not
be used. Similarly if A were also fitted with an astern gun it would be
able to attack its pursuer the whole time B was to its rear and in
this event, if its gun-fire were superior, it would be able to keep
the latter to a safe distance, or compel B to manoeuvre into a superior
position, which would entail a certain loss of time.

An astern firing gun would be valuable to B in another sense. Directly
it had passed A or brought the latter within the zone of its astern gun
it could maintain its fire at the most advantageous range, because owing
to its speed it would be able to dictate the distance over which shots
should be exchanged and if mounted with a superior weapon would be able
to keep beyond the range of A's guns while at the same time it would
keep A within range of its own gun and consequently rake the latter. In
the interests of self-preservation A would be compelled to change
its course; in fact, B would be able to drive it in any direction he
desired, as he would command A's movements by gun-fire.

The value of combined ahead and astern firing has been appreciated, but
there is one difficulty which at the moment appears to be insuperable
the clearance of the propeller. At the moment astern-firing, if such it
may be called, is maintained by repeating rifles, but this armament
is not to be compared with machine-gun firing, as the latter with
its capacity to pour 400 to 600 shots a minute, is far more deadly,
particularly when the weapon is manipulated by a crack gunner.

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