evidence: Karafuto Agency, from 1943 Karafuto Prefecture,[a] commonly known as South Sakhalin, was a part of the Empire of Japan on Sakhalin. It was part of the gaichi from 1907 to 1943 and later a prefecture as part of the naichi until 1945. Karafuto became a territory of the Empire of Japan in 1905 after the Russo-Japanese War, when the portion of Sakhalin south of 50°N was ceded from the Russian Empire in the Treaty of Portsmouth. Karafuto was established in 1907 as an external territory, until being upgraded to an "Inner Land" of the Japanese metropole in 1943. Ōtomari (Korsakov) was the capital of Karafuto from 1905 to 1908 and Toyohara (Yuzhno-Sakhalinsk) from 1908 to 1945. [...] In 1920, Karafuto was officially designated an external territory of Japan, and its administration and development came under the aegis of the Ministry of Colonial Affairs. Following the Nikolaevsk Incident in 1920, Japan briefly seized the northern half of Sakhalin, and occupied it until the establishment of formal diplomatic relations with the Soviet Union in 1925; however, Japan continued to maintain petroleum and coal concessions in northern Sakhalin until 1944. In 1943, the status of Karafuto was upgraded to that of an "inner land", making it an integral part of the Empire of Japan.