(A) ** Unrestricted submarine warfare against American civilians provoked the U.S.
(B) Germany used unrestricted submarine warfare in an attempt to invade the U.S.
(C) The U.S. developed unrestricted submarine warfare as a way to defeat Germany
(D) Unrestricted submarine warfare was needed by the U.S. to defend its own ports
EXPLANATIONS BELOW
Concept note-1: -Germany’s unrestricted submarine warfare strategy sent more merchant and passenger ships to the ocean’s floor and the loss of American lives mounted. The U.S. protested and in February severed diplomatic relations with Germany, while Congress appropriated funds for increased military affairs.
Concept note-2: -Germany’s resumption of unrestricted submarine warfare in February 1917, together with the Zimmermann Telegram, brought American entry into World War I on the British side. The Battle of the Atlantic during World War II.
Concept note-3: -The sinking of the Lusitania was the most notorious and deadly of several German submarine attacks in early 1917–attacks that were a key factor in the United States’ decision to abandon a policy of neutrality and enter the war.
Concept note-4: -Unrestricted submarine warfare is the practice of using submarines to attack and sink all forms of enemy shipping, whether they are military or civilian. It is most closely associated with the First World War when Germany’s decision to use USW brought the US into the war and led to their defeat.