 Finnish concessions and territorial losses exceeded those demanded by the Soviets pre @-@ war . Before the war , the Soviet Union demanded that the frontier between the USSR and Finland on the Karelian Isthmus be moved westward to a point only 30 kilometres ( 19 mi ) east of Viipuri , Finland 's second @-@ largest city , to the line between Koivisto and Lipola . In addition , the Finns would have to destroy all existing fortifications on the Karelian Isthmus . Finland should also cede to the Soviet Union the islands of Suursaari , Tytärsaari , and Koivisto in the Gulf of Finland . In the north , the Soviets demanded the Kalastajansaarento peninsula . Furthermore , the Finns should lease the Hanko Peninsula to the Soviets for thirty years , and permit the Soviets to establish a military base there . In exchange the Soviet Union would cede Repola and Porajärvi from Eastern Karelia , an area twice as large as the territories demanded from the Finns . 
