it referred to sinking ships
Unrestricted Submarine Warfare.
Order of events that describes changes in Germany's policy of unrestricted submarine warfare:unrestricted submarine warfareAmerican ultimatummoratoriumcancellation of the Sussex Pledge
This policy was called unrestricted submarine warfare
Serbia
announced its policy of unrestricted submarine warfare
In WW1, the German policy of unrestricted submarine warfare irritated neutral nations such as the United States and eventually helped public opinion to support the US entry into the war. In WW2 the German policy of unrestricted submarine warfare in the Atlantic irritated nominally neutral nations such as the United States and provided a rationale for increasing US support of Britain and its allies. In WW2 the American policy of unrestricted submarine warfare in the Pacific probably contributed to the degradation of Japanese economic capabilities as the war progressed.
Unrestricted submarine warfare (in the Atlantic).
the Zimmerman telegraph, Germany shooting down the Lusitania that had passengers on it and Germany's policy of unrestricted submarine warfare.
The German policy of unrestricted submarine warfare against shipping. This led to the sinking of the Lusitania in 1915. Great Britain and France were major trading partners.
"Unrestricted Submarine Warfare" was the policy followed by the German Navy to have German submarines without warning sink ships that were transporting food and other resources. U-boat was a term in WW1 referring to a submarine.
The US could no longer remain neutral in WWI because of Germany's policy of unrestricted submarine warfare and the Zimmerman note. Also, the United States had economic and cultural ties to the allies.