Conflict between Poland and Lithuania over possession of the city of Vilnius.
After World War I, the new Lithuanian government established itself at Vilnius. It was forced out by Soviet forces in 1919, and the city was then occupied by Polish forces (1919) and again by the Soviets, which ceded it to Lithuania in 1920. An armistice was arranged by the League of Nations, but Poland took Vilnius in 1920 and controlled the city and its surrounding region until they were restored to Lithuania in 1939.