The aim of this article is to examine the attitudes of the Soviet Union and Germany towards the problem of Vilnius in the period between the First and Second World Wars. The article is based mainly on unpublished documents from Lithuanian, Latvian, Estonian, German and Soviet archives. The problem under review emerged after the First World War, when Poland occupied the capital of Lithuania, Vilnius, and kept it under its control almost until the Second World War. Lithuania refused to recognize the situation, and between the two countries there arose a conflict, which was instigated by the Soviet Union and Germany, as they did not want the Baltic States and Poland to create a defence union.
The Soviet Union and Germany worked hand in hand in dealing with this conflict. In the process of its regulation they acquired quite an extensive experience in diplomatic co-operation, which they applied successfully in establishing the spheres of their influence in the Baltic States in 1939.