In World War I the German Army High Command believed that its military position was secure after the conquest of Rumania in the winter of 1916-1917, and that the time for unrestricted submarine warfare had therefore arrived. The High Command was wrong. read more
I am not sure it was a failure either time. Rather, the Germans depended excessively on what their U-boats of both periods could do well. The U-boats did extraordinary damage to Allied shipping and sank or disabled many military vessels. read more
The use of unrestricted submarine warfare was to have a major impact on World War One as it was one of the main reasons why America joined the war. When the German Chancellor Bethmann Hollweg announced Germany’s intention to use unrestricted submarine warfare, his one major concern and fear was that it would provoke an American response – in this he was to be correct. read more