Final answer:
Before signing the Sussex Pledge, Germany promised to stop unrestricted submarine warfare, which involved sinking neutral and noncombatant ships without warning. This decision was made following international outrage over the sinking of the Sussex, a French passenger ferry, by a German submarine. The compromise, however, was short-lived, with Germany resuming unrestricted warfare in 1917, thus prompting the U.S. entry into World War I.
Step-by-step explanation:
Before signing the Sussex Pledge, Germany made a compromise to refrain from unrestricted submarine warfare, which had led to the sinking of many neutral and noncombative ships. Germany's decision to engage in unrestricted submarine warfare had dire consequences, including the sinking of the Sussex – a French passenger ferry – in March 1916, which led to the injury and death of several American passengers.
The ensuing outcry from the United States, among other nations, led to Germany making a promise to the U.S. known as the Sussex Pledge. The compromise was that before sinking a ship, German U-boats had to provide for the safety of passengers and crew, and could not sink merchant vessels, only warships. This was a major step back from their previous unrestricted warfare policy.
Nonetheless, this pledge was ultimately fleeting. In a desperate attempt to win the war, Germany resumed unrestricted submarine warfare in early 1917, triggering the United States' entry into World War I.
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