HMS E9 and E11 sailed to force a passage in the Baltic, although E11 had to return home after a sighting by an enemy seaplane. HMS E1 then entered the Baltic and proceeded to Libau. Other submarines joined them at Lapvik, placed under the orders of the Russian Commander in Chief.
The Baltic Campaign
During January 1915, Ravel suffered a particularly cold spell. HMS E9 went to sea to discover if it was possible to patrol in the icy waters. Spray rapidly froze and formed ice up to six inches thick all over the exterior. The crew continually removed ice from the conning tower so that it could be closed in an emergency. However, when dived, the warmer salt water helped free the submarine from much of the ice.
The submarines steadily attacked German coastal shipping carrying vital war supplies. This forced the Germans to introduce a convoy system in their home waters. By their impact, real and imagined, the strategic effect of these boats on Germany was very significant. They harassed, and sometimes sank, German warships and dislocated the vital iron ore trade between Sweden and Germany which forced the commitment of even more German ships to anti-submarine duties. Their presence thwarted German naval advances in support of the land campaign against Russia. The Germans even blamed vessels lost to mines on British submarines. So successful were the British in 1915 and 1916 that German trade in the Baltic almost completely ceased.
The Baltic campaign ended in April 1918 after the Russians signed a peace treaty with Germany. The treaty demanded the surrender of all the British submarines, but the crews scuttled many of them before they could fall into German hands.