1920 - The division of Cieszyn and Cieszyn Silesia between Poland and Czechoslovakia

On November 5, 1818, the National Council of the Duchy of Cieszyn concluded an initial agreement with the Czech counterpart regarding the demarcation of Cieszyn Silesia using the criteria of ethnicity. The agreement was accepted by both governments. The greater part of Silesia was in the Polish zone, while the Czech zone included the area around Frýdek and Polish Ostrava. However, the Czechoslovak authorities could not really come to terms with these arrangements and on January 23, 1919, their army attacked the few Polish troops stationed in the area. After several days of fighting, the offensive was stopped at Skoczów. The weakness of Polish detachments resulted from the difficult military situation on the Polish-Ukrainian front. And this is when the Western powers became involved in the Cieszyn conflict. Eventually, the decision on Cieszyn Silesia was made during a conference at the Belgian resort of Spa. On 28.07.1920, the Council of Ambassadors divided Cieszyn Silesia and its capital between the two countries. The Polish part covered an area of ​​1002 km² (i.e. 44%), and the Czechoslovakian part was 1280 km² (i.e. 56%).