All four ships served with I Squadron of the German fleet for the first several years of their careers, with "Kurfürst Friedrich Wilhelm" the squadron flagship. During this period, they conducted routine training exercises and visited foreign countries, frequently in company with Kaiser Wilhelm II aboard his yacht. In 1900, they were deployed to China to help combat the Boxer Rebellion, but they arrived after the bulk of the fighting was over and thus saw little action there. After returning to Germany they were modernized beginning in 1902, thereafter resuming their peacetime activities. "Brandenburg" and "Wörth" remained in service with the German fleet until 1912, when they were laid up. In 1910, "Kurfürst Friedrich Wilhelm" and "Weissenburg" were sold to the Ottoman Navy and were renamed "Barbaros Hayreddin" and "Turgut Reis". The now-Ottoman ships saw extensive service during the First Balkan War, providing fire support to Ottoman ground forces fighting in Thrace, as well as engaging the Greek fleet at the Battles of Elli and Lemnos in December 1912 and January 1913, respectively.