Zaolzie (Czech Záolší (Zaolží), Slezsko zaolšanské, Polish Zaolzie, Śląsk zaolziański meaning Trans-Olza river) was the area disputed between Poland and Czechoslovakia West of Cieszyn with approximately 906 km² and 258,000 inhabitants.

In October 1918, following the end of First World War and the fall of Austro-Hungary, the area was divided between Poland and Czechoslovakia by two local self-government councils (Czech Narodni Vybor pro Slezsko and Polish Rada Narodowa). The majority of the area was taken over by Polish local authorities. In 1919 both councils were swallowed by the newly created and independent central governments in Prague and Warsaw. The former was not satisfied with the compromise and in 1919 started an offensive while Poland was engaged in war against Western Ukraine and bolshevik Russia. Eventually 66% of the area was then taken over by Czechoslovakia and according to the Spa conference in July 1920 the territory was officially annexed by Czechoslovakia.

In October 1938 the area was re-annexed by Poland, argumenting that Poles in Zaolzie deserves the same rights as Germans in the Munich Agreement, but on September 1, 1939 it was annexed by Germany after they invaded Poland. After 1945 the border returned to the line of 1920. On the 13 June 1958 in Warsaw both countries signed a treaty confirming the border on the line of 1 January 1938. Nowadays Zaolzie is a part of the Czech Republic and there is little tension between both countries.

See also

• Border conflicts between Poland and Czechoslovakia

External links

• The Birth of Czechoslovakia, 1914-1920