This was the German submarine warfare — ^the war with
mines and with submarines. Through the systematic
strategic employment of mines and submarines the
German naval leaders have in a short time succeeded
in making a continuous stay in the North Sea impossible
for the British main fleet. Only occasionally since last
fall have detachments of the English main fleet made



328 THE NAVY AND THE WAR

short» rapid sorties into the North Sea, only to return
immediately to the Irish Sea or to the waters west
and north of Scotland. This meant a shattering of
all English plans of a military blockade of the German
coasts, and of shutting the German naval forces up in
the German harbours. The British main fleet saw
itself unable to command the North Sea. Even the
mercantile blockade by British warships could not be
maintained, since the German submarines had become
too dangerous for the large British cruisers and other
warships. Therefore the British Admiralty established
a gigantic mine-field at the entrance to the North Sea
from the English Channel, and proclaimed other por-
tions of the North Sea a military zone which could be
traversed by neutral ships only at their own risk.
This was a violation of the rights of neutral shipping
unheard of in history; the neutrals have endured it.
