Imperial Russian Navy (IRN) had purchased German constructed submersibles built by the Germaniawerft shipyards out of Kiel. In 1903 Germany successfully completed its first fully functional engine-powered submarine, Forelle (Trout), and it was sold to Russia in 1904 and shipped via the Trans-Siberian Railway to the combat zone during the Russo-Japanese War.
Due to the naval blockade of Port Arthur, Russia sent their remaining submarines to Vladivostok, and by the end of 1904 seven subs were based there. On 1 January 1905, the IRN created the world’s first operational submarine fleet around these seven submarines. The first combat patrol sent out by the newly created IRN submarine fleet occurred on 14 February 1905 and was carried out by Delfin and Som, with each patrol normally lasting about 24 hours.
via English Russia