According to the Soviet–Lithuanian Mutual Assistance Treaty of October 1939, Lithuania agreed to allow some 20,000 of Soviets troops to be stationed at several bases within Lithuania in exchange for a portion of the Vilnius Region. Further Soviet actions to establish its dominance in its sphere of influence were delayed by the Winter War with Finland and resumed in spring 1940 when Germany was making rapid advances in western Europe. Despite the threat to the independence, Lithuanian authorities did little to plan for contingencies and were unprepared for the ultimatum.