Russia deployed an early submarine force from Vladivostok, yet its boats were neither fast to dive nor especially effective in attack. Japanese small craft could catch them on the surface and engage with quick-firing guns. The survival of most of the Som-class boats is therefore striking, but it also reinforced the belief that ordinary surface weapons remained an adequate answer. Only as batteries improved and submarines could remain hidden longer did detection and attack beneath the surface become the more urgent problem.
Notable Point · 31:57-34:01
The Russo-Japanese War and surface-era anti-submarine warfare
Early anti-submarine warfare often meant catching a slow-diving boat on the surface, not detecting it deep underwater.