1938
As Czechoslovakia was being absorbed into the German Reich, Zaolzie, the Czech half of Cieszyn, was annexed by Poland in 1938 following the Munich Agreement and the First Vienna Award. At noon on September 30, Poland gave an ultimatum to the Czechoslovak government. It demanded the immediate evacuation of Czech troops and police from Zaolzie and gave Prague until noon the following day. At 11:45 a.m. on October 1 the Czech foreign ministry called the Polish ambassador in Prague and told him that Poland could have what it wanted. Poland was accused of being an accomplice of Nazi Germany – a charge that Warsaw was hard put to deny.
Poland seized land from northern Spisz and northern Orawa, including territories around Suchá Hora and Hladovka, around Javorina, around Leśnica in the Pieniny Mountains, a small territory around Skalité, and some other very small border regions. They officially received the territories on 1 November 1938. Polish military groups began to carry out assimilation of the population. Polish was introduced as the only official language and the Slovak Intelligence were displaced from the territories.
Read more about this topic: Territorial Evolution Of Poland