The Kaiser's Legacy | Submarine Quandary
Intelligence | The Z-Plan
Submarine technology advanced swiftly in the First World War. One stealthy submerged submarine equipped with powerful torpedoes could easily destroy unsuspecting ships. International maritime nations bitterly protested. They demanded that U-boats follow prize rules set out in the Hague Conventions - as applied to surface warships. This prohibited an attack without warning, unless armed or in convoy.
In 1917 the Kaiser suddenly ordered total ‘unrestricted use’ of submarines. This almost tipped the outcome of the war in Germany’s favour. Entry of the United States against Germany helped extinguish the U-boat threat.
Before the Second World War international maritime nations declared unrestricted submarine strategy unacceptable. When war erupted in 1939, Germany had not considered U-boats as a premier naval weapon. Admiral Raeder had concentrated on surface warships and gave submarines a low priority in the Z-Plan.
Vice Admiral Karl Dönitz recognized the lack of German heavy ships to meet the allied challenge in 1939. As commander of the U-boat fleet he proposed that Germany immediately use all naval resources to build combat submarines. Raeder and Dönitz carried different strategic viewpoints throughout the war.