Amur - class minelayer ( 1898 ) The " Amur " - class minelayer s were the first purpose - built , ocean - going minelayers in the world . Both ships were constructed for the Imperial Russian Navy in the late 1890s . During the Russo - Japanese War of 1904 – 05 they were assigned to the Pacific Fleet . " Yenisei " struck one of her own mines two days after the war began while laying a minefield and sank . One of " Amur " s minefield s sank the Japanese pre - dreadnought battleship s and . " Amur " was sunk by Japanese howitzer s in December 1904 after the Japanese had gained control of the heights around Port Arthur . She was later salvaged and scrapped by the Japanese . Design and description . The " Amur " - class minelayers were designed to drop their mines while at high speed and were given a pronounced , overhanging , stern that allowed the mines to be dropped behind the propellers through doors in the stern . Each door was served by a rail that led directly to the mine storage compartments . The " Amur " - class ships were long at the waterline ; they had a beam of and a draft of . They had two pole masts and a ram bow . The ships had two vertical triple expansion steam engines , each powering one propeller . Twelve Belleville water - tube boilers provided steam . The engines were designed to produce a total of and gave the ship a top speed of . They carried of coal that provided a range of at a speed of . The main armament of the " Amur " - class ships consisted of five Canet Pattern 1892 50 - caliber guns . The gun fired shells to a range of about at its maximum elevation of 21° with a muzzle velocity of . The rate of fire was between twelve and fifteen rounds per minute . The ships also mounted seven Hotchkiss gun s . They fired a shell at a muzzle velocity of at a rate of 20 rounds per minute to a range of . The " Amur " - class ships mounted one torpedo tube and carried 300 mines . Service . Both ships , " Amur " and " Yenisei " , were built by the Baltic Works in Saint Petersburg . They were laid down in 1898 and completed the following year . They were assigned to the Pacific Fleet when the Russo - Japanese War began in 1904 and based in Port Arthur . Two days after the Japanese surprise attack on Port Arthur on 8 / 9 February 1904 , " Yenisei " was laying a minefield at Dalian Bay when one mine broke loose and began floating towards the ship . While maneuvering to avoid the mine " Yenisei " accidentally entered the minefield that she ' d just laid and hit a mine . The consequent explosion caused eight mines still on the rails to detonate , killing 96 or 100 crewmen and sinking the ship in 20 minutes . The protected cruiser and four destroyers responded to the incident , but " Boyarin " hit one of " Yenisei " s mines . The explosion flooded the ship ' s machinery spaces and her crew abandoned ship . The cruiser remained afloat , but foundered in Dalian Bay the next day during a storm . On the morning of 15 May 1904 , Rear Admiral Nashiba Tokioki led a squadron consisting of the pre - dreadnoughts " Hatsuse " , " Yashima " and to bombard Port Arthur . They encountered a field of 50 mines laid by " Amur " the evening before . " Hatsuse " hit one mine that disabled her engines and steering and drifted into another mine that caused one of her forward magazine s to detonate . The ship sank in about 90 seconds , taking 496 men down with her . " Yashima " struck another mine as she maneuvered around the drifting " Hatsuse " , but she was towed away from the minefield . By the late afternoon " Yashima " s flooding had become unstoppable and she was abandoned by her crew . Three hours later the ship capsized and sank . " Amur " was subsequently besieged in Port Arthur and hit in drydock a number of times by howitzer shells on 8 December 1904 . She was knocked over on her port side and rested on the side of the dock at an angle of 68° . On 18 December she was hit again by 30 shells and sunk on her side . The Japanese later raised the ship and scrapped it .