(A) the Zimmermann note
(B) ** unrestricted submarine warfare
(C) the invasion of Belgium
(D) German war atrocities
EXPLANATIONS BELOW
Concept note-1: -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.
Concept note-2: -Wilson cited Germany’s violation of its pledge to suspend unrestricted submarine warfare in the North Atlantic and the Mediterranean, as well as its attempts to entice Mexico into an alliance against the United States, as his reasons for declaring war.
Concept note-3: -The U.S. Navy adopted an official policy of unrestricted submarine warfare, and it appears the policy was executed without the knowledge or prior consent of the government. The London Naval Treaty, to which the U.S. was signatory, required submarines to abide by prize rules (commonly known as “cruiser rules").
Concept note-4: -World War I 4, 1915, Germany declared the waters around the British Isles a war zone in which Allied ships would be sunk, without warning if necessary. While this procedure dispensed with traditional civilities like boarding, search and seizure, and care of civilians, effective submarine warfare required it.
Concept note-5: -The American reaction to Germany’s announced intention of resuming unrestricted submarine warfare, violating the Sussex Pledge, was to declare war on Germany.