On 1 May 1915 the Cunard Liner RMS Lusitania, captained by Captain William Turner, left New York for Liverpool. The German Embassy to the USA took out advertisements in US newspapers warning passengers that the waters round the British Isles were a war zone in which merchant ships were liable to be sunk without warning. The German ad did not specifically mention the Lusitania or Cunard, but the most commonly reproduced version shows it to be placed below Cunard’s announcement of the departure times of its services to Liverpool.[1]

The day before the Lusitania sailed, the German U-boat U-20departed from Germany. Her captain, Kapitänleutnant Walther Schweiger, had orders to attack transports off Liverpool.[2] He had been in command when U20 sank three British merchants hips off Le Havre on 30 January, before the German declaration of unrestricted submarine warfare. He had also unsuccessfully tried…