Otto found himself in constant conflict with Duke Vladislav. Nevertheless, in 1123 he was able to succeed Vladislav's younger brother Soběslav as Prince of Brno. When Duke Vladislav died in 1125, Otto again claimed the Bohemian throne according to the principle of agnatic seniority. When Vladislav's brother Soběslav succeeded, Otto turned to King Lothair II who marched against Bohemia with a German army. Both sides met in the Battle of Chlumec on 18 February 1126: Lothair's forces were decisively defeated and Otto was killed in action. After the battle, Soběslav approached King Lothair and received the Bohemian duchy as an Imperial fief.