ed to dismantle its military base at Ootomari. Following the Opium War, Russia forced China to sign the Treaty of Aigun (1858) and Convention of Peking (1860), under which China lost to Russia all claims to all territories north of Heilongjiang (Amur) and east of Ussuri, including Sakhalin. A katorga (penal colony) was established by Russia on Sakhalin in 1857, but the southern part of the island was held by the Japanese until the 1875 Treaty of Saint Petersburg (1875), when they ceded it to Russia in exchange for the Kuril Islands.
Divided island
Sakhalin Island with Karafuto Prefecture highlighted
After the Russo-Japanese War, Russia and Japan signed the Treaty of Portsmouth of 1905, which saw the southern part of the island below 50th parallel north reverting to Japan; Russia retained the other three-fifths of the area. During the Siberian Intervention, Japan briefly held the northern part of the island from 1920 to 1925.
South Sakhalin was administrated by Japan as Karafuto Prefecture with the capital Toyohara, today's Yuzhno-Sakhalinsk, and had a large number of migrants from Korea.
The northern, Russian, half of the island formed Sakhalin Oblast, with the capital in Aleksandrovsk-Sakhalinsky.
Second World War
In August 1945, according to Yalta Conference agreements, the Soviet Union took over the control of Sakhalin. The Soviet attack on South Sakhalin was part of the Manchurian Strategic Offensive Operation and started on 11 August 1945, after the bombings of Hiroshima and Nagasaki and four days before the Surrender of Japan. The 56th Rifle Corps consisting of the 79th Rifle Division, the 2nd Rifle Brigade, the 5th Rifle Brigade and the 214 Armored Brigade attacked the Japanese 88th Division. Although the Red Army outnumbered the Japanese by a factor of three, they were unable to advance due to strong Japanese resistance.
It was not until the 113th Rifle Brigade and the 365th
