Submarines of the Imperial Japanese Navy
In 1904 Kawasaki Dockyard Company purchased plans for a modified version directly from Holland, and built two boats (Hulls No. 6 and 7), with the help of two American engineers, Chase and Herbert, who had been assistants to Holland. The Kawasaki-type submarines displaced 63 and 95 tons when submerged, and measured in overall length, respectively. both vessels measured at the beam. This contrasted with the original five imported Hollands-type submarines which had arrived that same year, at over 100 tons submerged, in overall length and beam. The Kawasaki Type #6 and #7 submarines had gained extra speed and reduced fuel consumption by . However both boats could launch only one torpedo, and each was manned by 14 sailors, whereas the imported Holland-type submarines could fire two torpedoes and could be operated by 13 sailors. This new type was designated the Type 6 submarine by the Imperial Japanese Navy, and was used primarily for test purposes.
Imperial Russian Navy
Due to the ongoing blockade of Port Arthur in 1904, the Imperial Russian Navy dispatched their remaining submarines to Vladivostok, and by the end of 1904 the last of seven subs had reached their new base there. Using the seven boats as a foundation, the Imperial Russian Navy created the world's first operational submarine fleet at Vladivostok on 1 January 1905. On 14 February 1905 the new "submarine fleet" sent out its first combat patrol consisting of the vessels "Som" and "Delfin". With patrols varying from 24 hours to a few days, the sub fleets first enemy contact occurred on 29 April 1905 when Imperial Japanese Navy torpedo boats fired upon "Som", withdrawing after failing to score a hit. On 1 July the Russian submarine "Keta" made contact with two Japanese torpedo boats in the Tartar Strait. "Keta" could not submerge quick enough to obtain a firing position and both adversaries broke contact.