On the route home, Conrad III and Frederick stopped in Thessaloniki where they swore oaths to uphold the treaty that Conrad had agreed with Emperor Manuel I Komnenos the previous winter. This treaty obligated the Germans to attack King Roger II of Sicily in cooperation with the Byzantines. After confirming the treaty, Frederick was sent ahead to Germany. He passed through Bulgaria and Hungary and arrived in Germany in April 1149. When Conrad died in February 1152, only Frederick and the prince-bishop of Bamberg were at his deathbed. Both asserted afterwards that Conrad had, in full possession of his mental powers, handed the royal insignia to Frederick and indicated that Frederick, rather than Conrad's own six-year-old son, the future Frederick IV, Duke of Swabia, succeed him as king. Frederick energetically pursued the crown and at Frankfurt on 4 March 1152 the kingdom's princely electors designated him as the next German king. He was crowned King of the Romans at Aachen several days later, on 9 March 1152. Frederick's father was from the Hohenstaufen family, and his mother was from the Welf family, the two most powerful families in Germany. The Hohenstaufens were often called Ghibellines, which derives from the Italianized name for Waiblingen castle, the family seat in Swabia; the Welfs, in a similar Italianization, were called Guelfs. The reigns of Henry IV and Henry V left the status of the German empire in disarray, its power waning under the weight of the Investiture controversy. For a quarter of a century following the death of Henry V in 1125, the German monarchy was largely a nominal title with no real power. The king was chosen by the princes, was given no resources outside those of his own duchy, and he was prevented from exercising any real authority or leadership in the realm. The royal title was furthermore passed from one family to another to preclude the development of any dynastic interest in the German crown. When Frederick I of Hohenstaufen was chosen as king in 1152, royal power had been in effective abeyance for over twenty-five years, and to a considerable degree for more than eighty years. The only real claim to wealth lay in the rich cities of northern Italy, which were still within the nominal control of the German king. The Salian line had died out with the death of Henry V in 1125. The German princes refused to give the crown to his nephew, the duke of Swabia, for fear he would try to regain the imperial power held by Henry V.