 In April 1938, the Soviets contacted the Finns, stating that they didn't trust Nazi Germany and wanted guarantees that Finland would not be used for the German attack on the USSR.In March 1939, the Soviets asked Finland to lease Suursaari and four small uninhabited islets for thirty years, and cede rich and heavily populated areas on the Karelian isthmus, saying that they were vital for the defense of Leningrad, the second biggest Soviet city.In return, the Soviet Union offered a large slice of empty and unofficially disputed Karelian borderland in exchange.