surface action, a strategy that culminated in the Battle of Jutland. Although the Germans claimed victory at Jutland, the British Grand Fleet remained in control at sea. Returning to effective anticommerce warfare by U-boats resumed. Vice Admiral Reinhard Scheer, commander in chief of the High Seas Fleet, pressed for all-out U-boat war, convinced that a high rate of shipping losses would force Britain to seek an early peace before the United States could react effectively. The renewed German campaign was effective, sinking 1.4 million tons of shipping between October 1916 and January 1917. Despite this, the political situation demanded even greater pressure, and on 31 January 1917, Germany announced that its U-boats would engage in unrestricted submarine warfare beginning 1 February. On 17 March, German submarines sank three American merchant vessels, and the U.S. declared war on Germany in April 1917. Unrestricted submarine warfare in early 1917 was initially very successful, sinking a major part of Britain-bound shipping. With the introduction of escorted convoys, shipping losses declined, and in the end, the German strategy failed to destroy sufficient Allied shipping. An armistice became effective on 11 November 1918. Of the surviving German submarines, 14 U-boats were scuttled and 122 surrendered. Of the 373 German submarines that had been built, 178 were lost by enemy action. Of these, 40 were sunk by mines, 30 by depth charges, and 13 by Q-ships; 512 officers and 4894 enlisted men were killed. They sank 10 battleships, 18 cruisers, and several smaller naval vessels. They further destroyed 5,708 merchant and fishing vessels for a total of 11,108,865 tons and the loss of about 15,000 sailors. The Pour le Mérite, the highest decoration for gallantry for officers, was awarded to 29 U-boat commanders. Twelve U-boat crewmen were decorated with the Goldene Militär-Verdienst-Kreuz, the highest bravery award for noncommissioned officers and enlisted men. The most successful U-boat commanders of World War I were Lothar von Arnauld de la Perière (189 merchant vessels and two gunboats with 446,708 tons), followed by Walter Forstmann (149 ships with 391,607 tons), and Max Valentiner (144 ships with 299,482 tons). Their records have not been surpassed in any subsequent conflict. Classes Körting kerosene-powered boats Type U 1, Type U 2, Type U 3, Type U 5, Type U 9, Type U 13, Type U 16, Type U 17 Mittel-U MAN diesel boats Type U 19, Type U 23, Type U 27, Type