Although the new Lithuanian government established itself at Vilnius in late 1918, it evacuated the city when Soviet forces moved in on January 5, 1919. A few months later Polish forces drove the Red Army out of Vilnius and occupied it themselves (April 20, 1919). The Lithuanians rejected the demands of the Polish chief of state, Józef Piłsudski, for union with Poland, and hostilities were avoided only by the Allies’ creation of a demarcation line (the Foch Line) to separate the armies of the two countries. Vilnius was left on the Polish side of the line.
In the summer of 1920, however, the Red Army reoccupied Vilnius, and on July 12 Soviet Russia ceded the city to Lithuania. Subsequently, violence broke out between Lithuania and Poland. The League of Nations arranged a partial armistice (October 7, 1920) that put Vilnius under Lithuanian control and called for negotiations to settle all the border disputes. Two days later Polish Gen. Lucjan Żeligowski drove the Lithuanian troops out, proclaimed the independence of central Lithuania, and established its government at Vilnius.
Poland and Lithuania would remain in a state of frozen conflict for the next 18 years. To frustrate Polish aspirations in the region, Lithuania financed Belarusian nationalists when portions of the Belorussian Soviet Socialist Republic were ceded to Poland after the Russo-Polish War. Negotiations between Poland and Lithuania continued under the aegis of the League of Nations, which finally abandoned its role as mediator on January 13, 1922. On January 8, 1922, however, General Żeligowski, again prompted by Piłsudski, called for elections for a regional Diet, which on February 20 voted to incorporate central Lithuania into Poland. That arrangement was later accepted by the League’s council, which set the border almost along the Foch Line (February 3, 1923)—a decision that was confirmed on March 15 by the conference of ambassadors of the Allied powers. Lithuania, however, rejected the settlement and, on the basis of the continuing Vilnius dispute, refused to arrange regular diplomatic relations with Poland. Only in 1938, under the pressure of a Polish ultimatum (issued March 17), did Lithuania agree to receive a Polish representative. Vilnius was restored to Lithuania on October 10, 1939.