of Reval through the autumn of 1915, departing on her first Baltic patrol on 21 September 1915. The following day she was in an excellent position to torpedo the German cruiser Bremen, but a surfaced Russian submarine caused the Bremen to turn away just as E18 was about to fire and the opportunity was lost; she returned to Reval on 29 September. On 9 October 1915 E18 departed for her second patrol, by 12 October she was in position to attack the pre-dreadnought SMS Braunschweig whilst off Libau (now Liepāja, Latvia), but her torpedo tube bow caps could not be opened. She then tried her beam tube but was forced to dive by German destroyers. When she did manage to fire a torpedo from her stern tube, the range was too great. She returned to Reval on 16 October.E18 departed Reval on 9 November 1915 to patrol the Swedish trade routes, returning on 15 November having sighted nothing of significance. During this patrol the crew had missed the visit of the Tzar. Her fourth and final patrol of 1915 was off Libau and try to find a way through the minefields by following the courses of German traffic. She departed for this patrol on 30 November and returned on 4 December. 1916 E18 left for her fifth patrol on 6 January 1916, her orders were to patrol the area between the Sound and Bornholm. Attempts were made to recall her, as the patrol had been cancelled but she did not reply. On returning, she encountered gale-force winds and icy conditions to the point where she had difficulty closing her conning tower hatch owing to ice. She was unable to return to Reval on her own and had to wait for the Finnish ice breaker Sampo to arrive and guide her in, completely iced over. The British submarines remained iced-in and could not move until April. Although she did not sail, E18 was made ready for sea by 13 February, and was the first of the British submarines to sail on 29 March after the freeze.E18 resumed patrols on 28 April, her penultimate patrol to the Gulf of Riga with HMS E1, to show their presence to the Germans, this was achieved by diving twice while Russian destroyers shelled beaches. While returning to Reval via Moon Sound on 1 May, E18 ran aground and had to be towed off. In late