As there isn't much collected together on this, I have put together a reasonably comprehensive answer. For most people, the links Mrs. Faithorn posted will be fine.
However, they only tell part of the story; indeed the Wikipedia site only mentions German and Austro-Hungarian submarines. There is a brief description of the U-Boat Campaign on the BBC History website
here. For information on British submarines have a look at
this page from the comprehensive History Learning Site. The Imperial War Museum has a
page on War at Sea in the twentieth century where you can listen to a sound recording of a British submariner from the First World War. For anyone who gets really into this, have a look at
this very detailed site.The following information on the German submarine campaign comes from a book published in 2003, 'The First World War: A New Illustrated History', by Hew Strachan. I have included this mainly for KS 4 and 5 students and condensed it somewhat.
Germany had started building submarines later than Britain and France, but this meant that by 1914 she was building better submarines at a faster rate. One of the most important effects of the U-Boats was to influence the British commander Jellicoe’s decision to turn away from the Germans at the Battle of Jutland in 1916.
Germany had too few submarines at the start of the war to sink enough merchant ships to knock Britain out of the war. However, if they could reduce trade and scare off shipping this would do nearly as well. Unfortunately, the rules of cruiser warfare stated that submarines had to surface, give a warning to the merchant ship and give the crew time to abandon ship. This much reduced the effectiveness of the U-Boats, especially when the British started to use disguised Q-ships which, when the U-Boat surfaced, opened fire with concealed guns.
Therefore, the Germans resorted to unrestricted submarine warfare from February to September 1915 when it was suspended because of the danger of bringing the United States into the war. However, by 1917 the Germans were so desperate that they again resorted to sinking all merchant ships without warning. With only about 30 U-Boats on station at any one time, the Germans managed to sink more than 600,000 tons of shipping each month from April to June.
However, the offensive failed: there were several reasons for this. Merchant ships were grouped into convoys which made the best use of Royal Navy destroyers, now freed from guarding the Grand Fleet. Now the USA was in the war (from April 1917) the US Navy also helped. The British had cracked the German naval signals code (Google
Room 40) and used more wirelesses to give up-to-date information about the whereabouts of U-Boats. Britain grew more food for itself than the Germans realised, especially after full-scale rationing was introduced in 1918. Finally, the Germans had assumed that ships from neutral countries would no longer carry supplies to Britain. However, because the British financial markets controlled freight rates and insurance of ships, neutral trade to Britain continued. Instead, less food was imported to neutral countries to be sent on to Germany.
“In this respect the Germans shot themselves in the foot: the U-boats campaign tightened the allied blockade.”
