When Germans began to settle in the 13th century, there was a systematic banishment of Bohemian influence and numerous local military conflicts erupted around strategically important fortifications. These fortifications primarily serve to protect the border and trading routes. Due to a lack of central power this protective function was left to local knights. The progressive division of the area due to the hereditary distribution of estates upset the economic balance of the region and many castles degenerated into bases for robber barons.