In preparation for the peace conference that was expected to follow World War I, in the spring of 1917 the British Foreign Office established a special section responsible for preparing background information for use by British delegates to the conference. Sakhalin is Number 56 in a series of more than 160 studies produced by the section, most of which were published after the conclusion of the 1919 Paris Peace Conference. Located in the Pacific off the coast of the Russian Far East and just north of Japan, Sakhalin was from 1875 to 1905 part of the Russian Empire, which mainly used it as a penal colony. The island was seized by Japan during the Russo-Japanese War of 1904−5 and, under the terms of the Treaty of Portsmouth ending the war, Russia ceded to Japan the southern part of the island. The two powers also agreed “not to construct in their respective possessions on the Island of Sakhaline or the adjacent Islands any fortifications or other similar military works.” The book includes sections on physical and political geography, political history, social and political conditions, and economic conditions. The study notes that the Russian population of the island had decreased in recent years, while the Japanese population had increased, mainly due to immigration from the Japanese mainland. The population of the indigenous peoples—mainly Gilyaks and Ainu—was also in decline. The Soviet Union regained the southern part of Sakhalin at the end of World War II, and Sakhalin (with the Kuril Islands) is now an oblast of the Russian Federation.