(A) ** Sinking of the Lusitania and Zimmerman Telegram
(B) U-Boats Submarine attack
(C) Gas Masks to protect soldiers from poisonous gas
(D) Zimmerman Telegram and Cuban missile Crisis
EXPLANATIONS BELOW
Concept note-1: -However, by 1917, the continued submarine attacks on U.S. merchant and passenger ships, and the “Zimmermann Telegram’s” implied threat of a German attack on the United States, swayed U.S. public opinion in support of a declaration of war.
Concept note-2: -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-3: -The Zimmermann telegram clearly had helped draw the United States into the war and thus changed the course of the war, which ended with an armistice, an agreement in which both sides agree to stop fighting, on November 11, 1918.
Concept note-4: -The telegram was considered perhaps Britain’s greatest intelligence coup of World War I and, coupled with American outrage over Germany’s resumption of unrestricted submarine warfare, was the tipping point persuading the U.S. to join the war.