level of security against the rising power of Nazi Germany. Negotiations In April 1938, NKVD agent Boris Yartsev contacted Finnish Foreign Minister Rudolf Holsti and Finnish Prime Minister Aimo Cajander, stating that the Soviets did not trust Germany and that war was considered possible between the two countries. The Red Army would not wait passively behind the border but would rather "advance to meet the enemy". Finnish representatives assured Yartsev that Finland was committed to a policy of neutrality and that the country would resist any armed incursion. Yartsev suggested that Finland cede or lease some islands in the Gulf of Finland along the seaward approaches to Leningrad, but Finland refused. Negotiations continued throughout 1938 without results. The Finnish reception of Soviet entreaties was decidedly cool, as the violent collectivisation and purges in Stalin's Soviet Union resulted in a poor opinion of the country. Most of the Finnish communist elite in the Soviet Union had been executed during the Great Purge, further tarnishing the Soviets' image in Finland. Meanwhile, Finland was attempting to negotiate a military co-operation plan with Sweden and hoping to jointly defend Åland. The Soviet Union and Nazi Germany signed the Molotov–Ribbentrop Pact in August 1939. It was publicly a non-aggression treaty, but it included a secret protocol in which eastern European countries were divided into spheres of interest. Finland fell into the Soviet sphere. On 1 September 1939, Germany began its invasion of Poland, and two days later, the United Kingdom and France declared war on Germany. On 17 September, the Soviets invaded Eastern Poland. Estonia, Latvia and Lithuania were soon forced to accept treaties that allowed the Soviets to establish military bases on their soil. Estonia accepted the ultimatum by signing the agreement on 28 September. Latvia and Lithuania followed in October. Unlike the three Baltic countries, Finland started a gradual mobilisation under the guise of "additional refresher training". The Soviets had already started intensive mobilisation near the Finnish border in 1938–39. Assault troops thought to be necessary for the invasion did not begin deployment until October 1939. Operational plans made in September called for the invasion to start in November. On 5 October 1939, the Soviets invited a Finnish delegation to Moscow for negotiations. Juho Kusti Paasikivi, the Finnish envoy to Sweden, was sent to Moscow to represent the Finnish government. The Soviet delegation demanded that the border between the USSR and Finland on