After the empire of Charlemagne was partitioned in 817 and 843, Alsace became part of Lotharingia, the kingdom of Lothair. In 925 Alsace became part of the German duchy of Swabia or Alemannia and was absorbed into the Holy Roman Empire, of which it remained a part for some 800 years. It remained a German possession until the 17th century, and during this period strong feudal principalities, controlled largely by the Habsburg rulers of Austria, emerged. A number of rich and powerful towns, such as Strasbourg and Colmar, developed in the late Middle Ages and won status as free towns or miniature republics. By the terms of the Peace of Westphalia in 1648, which concluded the Thirty Years' War, Alsace was placed under the sovereignty of France. Alsace constituted a province of the kingdom of France until the French Revolution (1789-1799), when Alsace was split into the departments of Bas-Rhin and Haut-Rhin. These departments, together with part of Lorraine, were incorporated into the German Empire after the Franco-Prussian War of 1870-1871.