Silesian tribes settled the lands at the end of the first millennium after the Migration Period. During the period of Germania Slavica, the region became part of Great Moravia under Svatopluk I of Moravia. Mieszko I brought the various existing Silesian duchies under the rule of the Piast dynasty and they became the Duchy of Silesia. It was again divided into small realms reigned by Silesian branches of Piast princes after the testament of Bolesław III Wrymouth in 1138. With the "Ostsiedlung", the cultural and ethnic Germanic influence grew with an influx of immigrants from the German-speaking areas of the Holy Roman Empire, of which Silesia was a direct part until the 1330s when it was subjugated to the Kingdom of Bohemia, then together with it became part of the Habsburg Monarchy (1526), then the Kingdom of Prussia (1742/44), and subsequently the German Empire (1871). In 1945, Lower Silesia was made part of Poland as agreed at the post-war Potsdam Conference. As a consequence, Lower Silesia suffered a nearly total loss of its pre-war population between 1945 and 1950. Polish citizens dispossessed by the Soviets were then settled in the now emptied lands.