British submarines were operational in the Baltic Sea throughout the First World War. Winston Churchill, then First Sea Lord, was keen to disrupt German naval operations in the area and hamper the export of iron ore from Sweden to Germany. A flotilla of Royal Navy submarines was attached to the Russian Baltic Fleet for this purpose; Russian navy liaison officers, telegraphists and signallers were assigned to co-ordinate operations.
In October 1914, submarines E1, E9 and E11 sailed from Harwich. Although E11 had to return with engine trouble, E1 and E19 reached Reval (now Tallinn) which was, at that time, a major naval base for the Imperial Russian Navy and a centre for Russian submarine operations in the Baltic. Successful operations prompted their reinforcement in September 1915 by E18 and E19, although E13 which had sailed with them ran aground at Saltholm and was destroyed by German torpedo boats with the loss of fifteen men. In October a further four of the smaller C-class boats (C26, C27, C32, and C35) were towed across the North Sea to Archangel and then by canal barge to St Petersburg; this tortuous journey and mechanical problems meant that they did not join the flotilla at Reval until the following year.
After the loss of E18 in June 1916, the flotilla continued to operate successfully through harsh conditions and the upheaval of the Bolshevik Revolution in 1917. Eventually, the German occupation of Reval in early 1918 forced them to move to Helsingfors (now Helsinki) and when German forces landed at Hango (now Hanko) the whole flotilla of eight submarines and three support ships (Cicero, Emilie, and Obsidian) was scuttled. The crews were evacuated home by sea and rail via Murmansk. Their Russian counterparts (AG12, AG16) were scuttled at Hango.
At Reval, covered in ice Photo: RN Submarine Museum