The House of Hohenstaufen

In 1125 the electors (the nobles who selected the rulers) chose Lothair, duke of Saxony, as the next monarch. Lothair's heir was his son-in-law, Henry Guelph (German: Welf), duke of Bavaria. After Lothair's death, however, the electors in 1138 chose Conrad III of the house of Hohenstaufen (also called Ghibelline after a family estate).

During Conrad's reign Henry Guelph's son, Henry the Lion, pushed German boundaries east along the Baltic seacoast with his conquest of Mecklenburg. The Saxon noble Albert the Bear Christianized the Wends. He inherited Brandenburg from the Wendish ruler and began colonizing it.

In 1152 Conrad was succeeded by his nephew Frederick I, called Barbarossa. Barbarossa was the outstanding Hohenstaufen ruler, although he failed in one of his lifetime objectives—to establish his authority over northern Italy. He ruled Germany with firmness and wisdom, encouraging learning, trade, the colonizing of eastern Germany, and the founding of towns. He made a duchy of Austria and added western Pomerania to his empire. When Henry the Lion failed to support him in his Italian wars, Barbarossa expelled the Guelphs from the duchies of Saxony and Bavaria.

Henry VI, Barbarossa's son, succeeded in 1190. His wife was heiress of Sicily. At Henry's death in 1197 his son was an infant and the throne was claimed by both Henry's brother Philip and Otto the son of Henry the Lion. Germany had civil war for almost 20 years. In 1212 Frederick II, son of Henry VI, became monarch. He ruled from Sicily and permitted the creation of numerous small principalities in Germany. Major commercial towns became free cities of the Hanseatic League. In the northeast the Teutonic Knights, a German religious order, began their conversion and conquest of the pagan Prussians.