the German submarine officers. Perhaps the most noticeable features of
the German submarines as a whole were their excellent engines and their
great strength of construction.

Prior to the month of February, 1917, it was the usual practice of the
enemy submarine in the warfare against merchant ships to give some
warning before delivering her attack. This was by no means a universal
rule, particularly in the case of British merchant vessels, as is
evidenced by the attacks on the _Lusitania, Arabic_, and scores of other
ships.

In the years 1915 and 1916, however, only 21 and 29 per cent.
respectively of the British merchant ships sunk by enemy submarines were
destroyed without warning, whilst during the first four months of the
unrestricted submarine warfare in 1917 the figure rose to 64 per cent.,
and went higher and higher as the months progressed.

Prior to February, 1917, the more general method of attack on ships was
to "bring them to" by means of gun-fire; they were then sunk by
gun-fire, torpedo, or bomb. This practice necessitated the submarine
being on the surface, and so gave a merchant ship defensively armed a
chance of replying to the gun-fire and of escaping, and it also gave
armed decoy ships a good opportunity of successful action if the
submarine could be induced to close to very short range.

The form of attack on commerce known as "unrestricted submarine warfare"
was commenced by Germany with the object of forcing Great Britain to
make peace by cutting off her supplies of food and raw material. It has
been acknowledged by Germans in high positions that the German Admiralty
considered that this form of warfare would achieve its object in a
comparatively short time, in fact in a matter of some five or six
months.

Experienced British naval officers, aware of the extent of the German
submarine building programme, and above all aware of the shadowy nature
of our existing means of defence against such a form of warfare, had
every reason to hold the view that the danger was great and that the
Allies were faced with a situation, fraught with the very gravest
possibilities.

The principal doubt was as to the ability of the enemy to train
submarine crews with sufficient rapidity to keep pace with his building
programme.

However, it was ascertained that the Germans had evidently devoted a
very great number of their submarines to training work during the period
September, 1915, to March, 1916, possibly i