of Austria, whereas most of Silesia became a part of Prussia. After the end of World War I, both of the two newly created independent states of Poland and Czechoslovakia claimed the area. Czechoslovakia claimed the area partly on historic and ethnic grounds, but especially on economic and strategic grounds. The area was important for the Czechs, as the crucial railway line connecting Czech Silesia with Slovakia crossed the area (the Košice–Bohumín Railway, which was one of only two railroads that linked the Czech provinces to Slovakia at that time). The western area of Cieszyn Silesia is also very rich in coal. Many important coal mines, facilities and metallurgy factories are located there. The Polish side based its claim to the area on ethnic criteria: a majority of the area's population was Polish according to the last (1910) Austrian census. Two local self-government councils, Polish and Czech, were created. Initially, both national councils claimed the whole of Cieszyn Silesia for themselves, the Polish Rada Narodowa Księstwa Cieszyńskiego in its declaration "Ludu śląski!" of 30 October 1918 and the Czech Národní výbor pro Slezsko in its declaration of 1 November 1918. On 31 October 1918, in the wake of World War I and the dissolution of Austria-Hungary, most of the area was taken over by local Polish authorities. The short-lived interim agreement of 2 November 1918 reflected the inability of the two national councils to come to final delimitation, and on 5 November 1918 the area was divided between Poland and Czechoslovakia by another interim agreement. In 1919 the councils were absorbed by the newly created and independent central governments in Prague and Warsaw. The former was not satisfied with the situation and on 23 January 1919 invaded the area while both parties were engaged in much larger conflicts elsewhere, Poland in its war against the West Ukrainian National Republic and Czechoslovakia in the war with the Hungarian Soviet Republic over Upper Hungary. The impetus for the Czech invasion in 1919 was Poland's organising of elections to the Sejm (parliament) of Poland in the disputed area. The elections were to be held in the whole of Cieszyn Silesia. The Czechs claimed that the polls must not be held in the disputed area, as the delimitation was only interim and no sovereign rule should be executed there by any party. The Czech demand was rejected by the Poles and, following the rejection,