On what basis did the british respond negatively to the german decision to initiate submarine warfare during world war i?

Even after Germany announced its resumption of submarine warfare in January 1917, President Wilson continued to hope for a negotiated peace. But in February 1917, British authorities told him about a telegram that the German foreign secretary, Arthur Zimmermann, had sent to the German minister in Mexico, proposing that in the event of war between Germany and the United States, Germany would restore to Mexico the territory it lost inthe Mexican War if Mexico would declare war against the United States. President Wilson felt that this attempt to spread the war into the Western Hemisphere was intolerable, and it led him toask Congress to approve a policy allowing merchant ships to fight back against attackers. The surface ships used in conventional warfare could confiscate freighters or prevent them from entering a war zone. Submarines, however, took the tactic of surprising and sinking enemy vessels and did not have the room to pick up survivors. The Britishdeclared that Germany’s use of U-boats violated principles of “civilized” warfare