January 23: The German battle cruiser squadron moved out to raid the English coast and aggravate the British fishing fleet. In the ensuing battle, the Germans lost one cruiser and both flagships were damaged. Through misunderstanding of signals, the British pursuit was not vigorous, and the remaining German ships got away.
February 4: Submarine warfare intensified when Germany initiated a campaign against Allied merchant ships in waters surrounding the British Isles. They also attacked a number of neutral vessels.
May 7: The British luxury liner Lusitania was torpedoed without warning by a U-boat off the Irish coast. Among the 1,198 lost were 124 Americans leading to a controversy between the United States and Germany that almost precipitated war between the two nations. The firm stand taken by the U.S. forced Germany to modify its method of submarine warfare to the satisfaction of the American government.
August 19: The British liner Arabic was sunk, with the loss of four more Americans. Reaction in the United States became so hostile that on 1 September, Germany announced cessation of unlimited submarine warfare. By the end of 1915 German U-boats had destroyed almost one million tons of Allied shipping.