Silesian German

The Silesian Germans speak an East Central German dialect brought to the Oder by the Ostsiedlung. West Slavic Silesia joined Piast Poland under Mieszko I around 990, but from the early thirteenth century Duke Henry the Bearded invited German settlers; Breslau became German-speaking while Polish peasants kept their own language. The Mongol victory at Legnica in 1241, where Henry II the Pious fell, spurred immigration.

The 1335 Treaty of Trentschin placed Silesia under the Bohemian Crown, which also ruled Upper Lusatia, whose six cities formed the Lusatian League in 1346. Both passed to the Habsburgs in 1526, turned Lutheran in the 1520s, and suffered the Thirty Years' War.

The 1635 Peace of Prague gave Upper Lusatia to Saxony, while Frederick II of Prussia conquered Silesia in 1742; the 1815 Congress of Vienna created the Prussian Province of Silesia, attaching a slice of Upper Lusatia with Görlitz.