The Soviet Union had demanded from Finland a military base in the writing of regional exchange requirements just before outbreak of the
Winter War from Hanko peninsula. In October 1939
Geoffrey Cox was told that the Finnish General Staff were prepared to cede even the
Petsamo area, but not Hanko, which they knew in Russian hands would be
a pistol pressed into Finland’s back, and which was the
real key to the Gulf of Finland. The Russians were prepared to hand over in return
some territory just north of the Finnish “waist-line”: - stretches of forest of no military value. After the Winter War, in the early Spring of 1940, the
Soviet Union repeated its call for a naval base in the Hanko area. Finland's negotiation delegation was forced to agree to the Soviet Union's peace terms, including the Hanko base. On March 12, 1940, the
Moscow Peace Treaty included a lease to the Soviet Union, for 30 years, of 115 square kilometers of territory which included the area of the Hanko Peninsula and the city of
Hanko surrounding maritime areas, as well as about 400 islands. The area was handed over to the Soviets at Midnight on 22 March 1940. The Finnish population had been evacuated from the area, causing about 8,000 Finns to lose their homes. Soviet Union forces built a strong military base. It oversaw maritime traffic in the
Gulf of Finland, and was also a potential south-west invasion front for war against Finland. The base housed infantry, airborne and armored forces. The Soviet Union fortified the border between Finland and the base, and the Finnish forces invested in troops and fortifications on their side. ==Outbreak of the Continuation War ==