Unrestricted submarine warfare applied siege logic to an island economy by attacking the shipping that brought in food, raw materials, and war supplies. Mines and submarine attacks offered Germany a way to exert pressure that the High Seas Fleet could not impose directly. The method raised immediate problems over neutral vessels, civilian deaths, and diplomatic reaction, especially after the Lusitania sinking. Earlier, interrupted experiments with submarine warfare also warned Britain that a more comprehensive campaign might follow. An earlier attack would have faced a less-prepared opponent. Germany then lacked the submarine force needed to sustain it.
Chapter · 27:09-30:02
Using submarines to blockade Britain
The strategic object of unrestricted submarine warfare was to reverse Britain's pressure on Germany by cutting an island economy off from seaborne trade.