After its annexation to Poland, Jews of the Těšín region were often denied certificates of Polish citizenship, were registered as foreigners and then usually deported. There were leaflets calling for a boycott of Jewish shops, leaflets with anti-Jewish slogans such as “Jew is the enemy" ("Żyd to wróg"), “Not a penny to the Jew" ("Ani grosza do Żyda") or "Buy only from Poles" ("Kupuj tylko u Polaków”) appeared. The first bomb attack on a Jewish building in Czechoslovakia took place in Třinec at the end of September 1938, when local Polish nationalists blew up part of the outbuildings near the synagogue, which they considered to be Czech objects, a manifestation of the Czech occupation of the region.
The photo from an old postcard shows the synagogue in Třinec on the left. OpenEye archive.