In October 1914, the first British submarines joined the Russian Baltic Fleet. Out of three boats only two, the E9 and E1, succeeded in completing the hazardous journey through the Sound (a stretch of water separating Denmark from Sweden) to Reval in the Gulf of Finland. In 1915 further submarines, both E class and the smaller C class, made their way to Reval, with several running aground, with the E13 beached on the neutral Danish island of Saltholm. Between 1914–18 British submarines successfully intercepted and sunk German ships importing ore from Sweden to Germany. Despite several hitting mines or being torpedoed, they also helped confine German vessels to their bases and prevented the region being used for German training exercises. On 1 March 1918, the British flotilla moved to Helsinki (Helsingfors), after the German occupation of northern Estonia. Here, the submarines were placed under the protection of Finnish communists.