iom of war that new weapons of attack are invariably met
by new methods of defence. So it was with the convoy system which gave
the death-blow to German hopes of a submarine victory. In order to
understand this _new_ method it is necessary to study the accompanying
diagram, which, however simple it may appear on paper, is extremely
difficult to carry out in practice.

At each great port there was a convoy officer, who assembled the
merchant ships when they had been loaded and explained to their captains
the exact position each ship was to occupy when the fleet was at sea.
Printed instructions were handed round urging each vessel to keep its
correct station, stating the procedure to be adopted in the event of an
engine breakdown, giving the manoeuvres which were instantly to be
carried into effect when an attack was threatened, and finally the
special signals arranged for communication between the merchantmen and
their escort by day and by night.

The number of vessels composing a convoy varied, but often exceeded
twenty big cargo ships, carrying some 120,000 tons of merchandise, or
six liners, with 20,000 troops on board, while the escorting flotilla
consisted of a light cruiser, acting as flag-ship, six destroyers, two
special vessels ("P" boats) towing observation airships, and some eight
or ten trawlers, with possibly one or more seaplanes and several M.L.'s
for the first few miles of the voyage. The destroyers were spread out
ahead and on the flanks of the fleet, and by using their greatly
superior speed were able to zigzag and circle round the whole convoy.

[Illustration: FIG. 18.--Diagram showing the disposition of a convoy of
troops, munitions or food.]

In the event of an attack the whole fleet turned off from the course
they were steering at a sharp angle, showing only their sterns to the
U-boat. A destroyer acted as rearguard to prevent any of the convoyed
ships from straggling. When the fleet had arrived at a rendezvous far
out in the open sea, where the danger of a submarine attack was much
less, the escort handed over their charges to one or two ocean-going
cruisers, which stayed with the merchant ships throughout the remainder
of their voyage.

[Illustration: A MOTOR LAUNCH CLEARED FOR ACTION

_Yachting Monthly_]

The escorting flotilla then cruised about in the vicinity of the
rendezvous until an incoming convoy appeared. These ships were then
taken over from their mid-ocean cruiser guard and esc