torpedoed by the German submarine SM U-86 on 27 June 1918 in violation of international law. Only 24 of the 258 medical personnel, patients, and crew survived. Survivors reported that the U-boat surfaced and ran down the lifeboats, machine-gunning survivors in the water. The U-boat captain, Helmut Brümmer-Patzig, was charged with war crimes in Germany following the war, but escaped prosecution by going to the Free City of Danzig, beyond the jurisdiction of German courts. Blockade of Germany After the war, the German government claimed that approximately 763,000 German civilians died from starvation and disease during the war because of the Allied blockade. An academic study done in 1928 put the death toll at 424,000. Germany protested that the Allies had used starvation as a weapon of war. Sally Marks argued that the German accounts of a hunger blockade are a "myth," as Germany did not face the starvation level of Belgium and the regions of Poland and northern France that it occupied. According to the British judge and legal philosopher Patrick Devlin, "The War Orders given by the Admiralty on 26 August [1914] were clear enough. All food consigned to Germany through neutral ports was to be captured and all food consigned to Rotterdam was to be presumed consigned to Germany." According to Devlin, this was a serious breach of International Law, equivalent to German minelaying. Chemical weapons in warfare The German army was the first to successfully deploy chemical weapons during the Second Battle of Ypres (22 April – 25 May 1915), after German scientists working under the direction of Fritz Haber at the Kaiser Wilhelm Institute developed a method to weaponize chlorine. The use of chemical weapons was sanctioned by the German High Command in an effort to force Allied soldiers out of their entrenched positions, complementing rather than supplanting more lethal conventional weapons. In time, chemical weapons were deployed by all major belligerents throughout the war, inflicting approximately 1.3 million casualties, but relatively few fatalities: About 90,000 in total. For example, there were an estimated 186,000 British chemical weapons casualties during the war (80% of which were the result of exposure to the vesicant sulfur mustard, introduced to the battlefield by the Germans in July 1917, which burns the skin at any point of contact and inflicts more severe lung damage than chlorine or phosgene), and up to one-third of American casualties were caused by them.