Unrestricted submarine warfare

There have been attempts to limit the use of unrestricted naval warfare, with some dating back to before the turn of the 20th century as an extension of rules for surface raiders.

[2] However, the Imperial German navy was heavily criticised internally by high level officials for their relative inactivity at the start of WWI.

The admirals appealed to public opinion through press interviews,[3] posing the submarines as "miracle weapons", despite the extremely small number of vessels available.

It was believed that a "shock effect" would cause shipping to cease, and that neutrals would judge the campaign a reasonable reprisal for the British naval blockade.

However, the German Admiralty encouraged the U-boats to attack without warning and minimise efforts at identifying targets, as "accidental" sinking of neutral vessels was viewed to have a useful deterrent effect.

In the end, the German campaign did not have a significant impact on Britain's goods traffic, but took a heavy civilian toll, including to neutrals.

[7][8] The decision made by Germany became one of the "trigger mechanisms" causing the United States, who were previously neutral, to join the war in favour of the British.