may 21, 1666 - The Holy Roman Empire, ruled by Leopold I, repurchases the territory of the Duchy of Opole and Racibórz (Oppeln und Ratibor), which it had ceded to Poland in 1645, for the sum of 120,000 guldens and consolidates it with Upper Silesia. The territory will be ceded from Germany to Poland in 1945 at the end of World War II