signed a peace treaty. Boleslaus I agreed to resume paying tribute and to recognize Otto I as his overlord. The Duchy was then incorporated into the Holy Roman Empire as a constituent state. Bohemia would be a major factor in the many battles along the Empire's eastern border. Boleslaus I helped Otto I crush an uprising of Slavs along the Lower Elbe in 953, and they joined forces again to defeat the Hungarians at the battle of Lechfeld in 955. In 973 Otto I established the bishopric of Prague, subordinated to the archbishopric of Mainz, in order to Christianize the Czech territory. To strengthen the Bohemian-Polish alliance, Boleslaus I's daughter Dobrawa was married to the pagan Mieszko I of Poland in 965. The marriage helped bring Christianity to Poland. He died in 972 and was succeeded as Duke by his oldest son Boleslaus II. After initially siding with Henry II against Otto II during Henry's failed revolt in 977, Boleslaus II swore loyalty to Otto II. When Otto II died suddenly in 983 and was succeeded by the three-year old Otto III, Boleslaus II again supported Henry II in his bid for the German throne. As in 977, Henry's bid failed, and Boleslaus II swore loyalty to Otto III. Hungarian relations Otto I's defeat of the Hungarians at Lechfeld in 955 ended the decades-long Hungarian invasions of Europe. The Hungarian Grand Prince Fajsz was deposed following the defeat and was succeeded by Taksony, who adopted the policy of isolation from the West. He was succeeded by his son Géza in 972, who sent envoys to Otto I in 973. Géza was baptised in 972, and Christianity spread among the Hungarians during his reign. Géza expanded his rule over the territories west of the Danube and the Garam, but significant parts of the Carpathian Basin still remained under the rule of local tribal leaders. In 997, Géza died and was succeeded by Stephen (originally called Vajk). Stephen was baptized by Bishop Adalbert of Prague and married Gisela, daughter of Henry II and distant niece of Otto III. Stephen had to face the rebellion of his relative, Koppány, who claimed Géza's inheritance based on the Hungarian tradition of agnatic seniority. Stephen defeated Koppány using some Western tactics and a small number of Swabian knights. When Otto III traveled to Poland in 1000, he brought with him a crown from Pope Sylvester II.