Short answers, pulled from the story.
Sakhalin is the largest island in Russia, with an area of 72,492 square kilometres, located in Northeast Asia. Its northern coast lies 6.5 km from the southeastern coast of Khabarovsk Krai, while its southern tip sits 40 km north of Japan's Hokkaido. It separates the Sea of Okhotsk to its east from the Sea of Japan to its southwest.
Sakhalin derives from the Manchu word Sahaliyan, meaning "black," which is the proper Manchu name of the Amur River. The Manchus called the island Sahaliyan ula angga hada, meaning "Island at the Mouth of the Black River." The word was borrowed into Russian as Sakhalin.
Anton Chekhov visited the Russian penal colony on Sakhalin in 1890 and spent three months there interviewing thousands of convicts and settlers for a census. He published his findings in the memoir Sakhalin Island, which brought the conditions of the katorga system to wide literary attention. The colony had been formally established as a site of hard labor after Tsar Alexander II approved the relevant regulations on the 18th of April 1869.
The Soviet Union invaded southern Sakhalin beginning on the 11th of August 1945, a few days before Japan's surrender, in an operation planned secretly at the Yalta Conference. The Soviets completed the conquest on the 25th of August 1945 by occupying the capital Toyohara. Of the approximately 400,000 people who lived in South Sakhalin in 1944, about 100,000 were evacuated to Japan, and 279,356 residents were repatriated between December 1946 and July 1949.
On the 1st of September 1983, Korean Air Flight 007, a South Korean civilian airliner, was shot down by the Soviet Union just west of Sakhalin Island near Moneron Island. All 269 passengers and crew died, including U.S. Congressman Larry McDonald. Soviet commanders had recognized the aircraft as commercial before it was destroyed.
Sakhalin holds an estimated 14 billion barrels of oil and 2,700 cubic kilometres of natural gas, developed under production-sharing agreements with companies including ExxonMobil and Shell. Two major consortia, Sakhalin-I and Sakhalin-II, signed exploration contracts in 1996 with a combined initial cost estimate of $21 billion. Gazprom later acquired a 50% plus one share in the Sakhalin II project.