In January 1917, the Germans initiated a new policy of unrestricted submarine warfare against ships in the seas around the British Isles. German leaders knew that the policy would likely provoke U.S. entrance into the war, but they hoped to defeat the Allied Powers before the U.S. could fully mobilize. In late February, the U.S. public learned of the Zimmermann Telegram, a secret diplomatic communication in which Germany sought to convince Mexico to join it in a war against the United States. After a series of attacks on American ships, Wilson held a Cabinet meeting on March 20; all Cabinet members agreed that the time had come for the United States to enter the war. The Cabinet members believed that Germany was engaged in a commercial war against the United States, and that the United States had to respond with a formal declaration of war.