On the afternoon of 7 May, a German U-boat torpedoed "Lusitania" off the southern coast of Ireland inside the declared war zone. A second internal explosion sank her in 18 minutes, killing 1,198 passengers and crew. The German government justified treating "Lusitania" as a naval vessel because she was carrying 173 tons of war munitions and ammunition, making her a legitimate military target, and they argued that British merchant ships had violated the cruiser rules from the very beginning of the war. The internationally recognized cruiser rules were obsolete by 1915; it had become more dangerous for submarines to surface and give warning with the introduction of Q-ships in 1915 by the Royal Navy, which were armed with concealed deck guns. The Germans argued that "Lusitania" was regularly transporting "war munitions"; she operated under the control of the Admiralty; she could be converted into an armed auxiliary cruiser to join the war; her identity had been disguised; and she flew no flags. They claimed that she was a non-neutral vessel in a declared war zone, with orders to evade capture and ram challenging submarines.