conflict with Otto I's Kingdom of Germany, who also desired to conquer the Polabian Slavs. Otto I sent his trusted lieutenant, the Saxon Margrave Gero, to address the Polan threat, while Otto I traveled to Italy to be crowned as emperor. Gero defeated Mieszko I in 963 and forced him to recognize Otto I as his overlord. In return for submitting tribute to the newly crowned Emperor, Otto I granted Mieszko I the title of amicus imperatoris ("Friend of the Emperor") and acknowledged his position as dux Poloniae ("Duke of Poland"). Mieszko I remained a powerful ally of Otto I for the remainder of his life. He strengthened his alliance with the Empire by marrying Oda, the daughter of the Saxon Margrave Dietrich of Haldensleben, in 978 and by marrying his son Bolesław I to a daughter of Margrave Rikdag of Meissen. Mieszko I, then a pagan, would marry the Christian daughter of Boleslaus I, Dobrawa, in 965 and would convert to Christianity in 966, bringing Poland closer to the Christian states of Bohemia and the Empire. Following the death of Otto I in 973, Mieszko I sided with Henry II, Duke of Bavaria, against Otto II during Henry's failed revolt in 977. After the revolt was put down, Mieszko I swore loyalty to Otto II. When Otto II died suddenly in 983 and was succeeded by the three-year old Otto III, Mieszko I again supported Henry II in his bid for the German throne. When Henry's revolt failed, Mieszko I swore loyalty to Otto III. Mieszko I's son Bolesław I succeeded him as Duke in 992, and Poland continued its alliance with the Empire. Polish forces joined the Empire's campaigns to put down the Great Slav Rising, led by the Polabian Lutici tribes during the 980s and 990s. Bohemian relations Germany and the Duchy of Bohemia came into significant contact with one another in 929, when German King Henry I had invaded the Duchy to force Duke Wenceslaus I to pay regular tribute to Germany. When Wenceslaus I was assassinated in 935, his brother Boleslaus I succeeded him as Duke and refused to continue paying the annual tribute to Germany. This action caused Henry I's son and successor Otto I to launch an invasion of Bohemia. Following the initial invasion, the conflict deteriorated into a series of border raids that lasted until 950 when Otto I and Boleslaus I