The leaders of the Babenbergs were the sons of Duke Henry, who called themselves after their castle of Babenburg on the upper Main river, around which their possessions centred. The city of Bamberg was built around the ancestral castle of the family. The Conradines were led by Conrad the Elder and his brothers Rudolf and Gebhard, probably the sons of Count Udo of Neustria. The rivalry between the Babenberg and Conradine families was intensified by their efforts to extend their authority in the region of the middle Main, and this quarrel, known as the "Babenberg feud", came to a first head in 892, when King Arnulf deposed Poppo II as Thuringian ruler, appointing Conrad the Elder instead, and installed Conrad's brother Rudolf as Bishop of Würzburg. The struggle intensified at the beginning of the 10th century during the troubled reign of Arnulf's son King Louis the Child. Clashes of arms occurred in 902, when the Conradine laid siege to Babenburg Castle and arrested Adalhard of Babenberg. The next year, Adalhard was executed at the "Reichstag" of Forchheim; in return, the Babenbergs occupied the city of Würzburg and expelled Bishop Rudolf. Meanwhile Rudolf's brother Gebhard was appointed Duke of Lotharingia in 903, and had to cope both with revolting nobles and the continuing attacks by Babenberg forces. Both sides met in the battle of Fritzlar on 27 February 906, where the Conradines won a decisive victory, although Conrad the Elder fell in the battle. Two of the Babenberg brothers were also killed. The third, Adalbert, was summoned before the imperial court by the regent Archbishop Hatto I of Mainz, a partisan of the Conradines. He refused to appear, held his own for a time in his castle at Theres against the king's forces, but surrendered in 906, and in spite of a promise of safe-conduct by Hatto was beheaded. Conrad the Younger became Duke of Franconia in 906 and King of East Francia (as Conrad I) in 911, while the Babenbergs lost their influence in Franconia. In 962 the Bavarian count Leopold I ("Liupo"), possibly a descendant of the Luitpolding duke Arnulf of Bavaria, was first mentioned as a faithful follower of Emperor Otto I. He remained a loyal supporter of Otto's son and successor Otto II and in 976 appears as count of the Bavarian Eastern March, then a district not more than 60 miles in breadth on the eastern frontier of the duchy, which grew into the Margraviate of Austria.