At the start of 1917, the Allies, most notably Great Britain, were threatened
with the full force of a devastating weapon. The Germans decided to use
unrestricted submarine warfare against merchant shipping. In order to capitahze
on the submarine's advantages of stealth and surprise, the Germans
attacked, without warning, both Allied vessels and ships bearing the flag of
neutral countries. The Germans concentrated their effort in a wide zone around
the British Isles, hoping to close off shipping lanes and to shut down Britain's
ability to wage war. The use of the new technology of the submarine raised
new questions about the rights of neutrals and the "rules" of the sea. It also
led to rethinking the nature of naval warfare in the modem age.
For all the vast expenditures of 1914, the huge naval armadas and even
their individual vessels only rarely saw action. To the surprise of all
authorities, the naval war took a novel turn. The submarine war—as the
Germans used the new weapon to strike at Allied commerce, and their
opponents sought desperately to find effective countermeasures—became
the centerpiece of naval operations for the final two years of the war. As
U-boats hunted their prey and Allied surface forces sought to combat the
Germans, the course of the entire war at sea hung in the balance.