Zaolzie is the Polish name for an area now in the
Czech Republic which was disputed between
interwar Poland and
Czechoslovakia. The name means "lands beyond the
Olza River"; it is also called
Slask zaolzianski, meaning "trans-Olza
Silesia". Equivalent terms in other languages include
Zaolší (Zaolží) in Czech and
Olsa-Gebiet in German. The Zaolzie region was created in 1920, when
Cieszyn Silesia was divided between Czechoslovakia and Poland. Zaolzie forms the eastern part of the Czech portion of Cieszyn Silesia. The division did not satisfy any side, and persisting conflict over the region led to its annexation by Poland in October 1938, following the
Munich Agreement. After German invasion of Poland in 1939, the area became a part of Nazi Germany until 1945. After the war, the 1920 borders were restored.