The flotilla was established as part of the Pacific Fleet in August 1939 to guard coastal and maritime communications in the Strait of Tartary and the Sea of Okhotsk, with its main base at Sovetskaya Gavan, under the command of Counter Admiral Mikhail Arapov.
[2] Subordinated to the 2nd Far Eastern Front for the war, the flotilla laid minefields in the Strait of Tartary and the Sakhalin Gulf beginning on the evening of 8 August in order to prevent Japanese retaliation.
[4] It was tasked with supporting an amphibious landing by the 365th Battalion and the 113th Rifle Brigade at the ports of Toro and Maoka, departing from Sovetskaya Gavan.
This was followed by the 20 August landing of 3,400 men from the remainder of the 113th Brigade and a battalion of sailors at Maoka, which speedily defeated the Japanese defenders.
[6] The flotilla subsequently participated in the Invasion of the Kuril Islands and the Sungari Offensive during the Soviet–Japanese War, providing transport and launching air strikes on Japanese bases and ports.