of Poland in the 10th century. However, already Mieszko II Lambert (1025 ~ 1034) effectively lost control over the area and had to accept German suzerainty over the area of the Oder lagoon. Subsequent Polish rulers, the Holy Roman Empire, and the Liutician federation all aimed to control the territory. After the decline of the neighbouring regional centre Wolin in the 12th century, the city became one of the more important and powerful seaports of the Baltic Sea. In a campaign in the winter of 1121–1122, Bolesław III Wrymouth, the Duke of Poland, gained control of the region, including the city of Szczecin and its stronghold. The Polish ruler initiated Christianization, entrusting this task to Otto of Bamberg, and the inhabitants were Christianised by two missions of Otto in 1124 and 1128. At this time, the first Christian church of Ss Peter and Paul was erected. The Poles' minted coins were commonly used in trade in this period. The population of the city at that time is estimated to be at around 5,000–9,000 people. Polish rule ended with Boleslaw's death in 1138. During the Wendish Crusade in 1147, a contingent led by the German margrave Albert the Bear, an enemy of Slavic presence in the region, papal legate, bishop Anselm of Havelberg and Konrad of Meissen besieged the town. There, a Polish contingent supplied by Mieszko III the Old joined the crusaders. However, the citizens had placed crosses around the fortifications, indicating they already had been Christianised. Duke Ratibor I of Pomerania, negotiated the disbanding of the crusading forces. After the Battle of Verchen in 1164, Szczecin duke Bogusław I, Duke of Pomerania became a vassal of the Duchy of Saxony's Henry the Lion. In 1173, Szczecin castellan Wartislaw II, could not resist a Danish attack and became vassal of Denmark. In 1181, Bogusław became a vassal of the Holy Roman Empire. In 1185, Bogusław again became a Danish vassal. Despite falling under foreign suzerainty, local dukes maintained close ties with the fragmented Polish realm, and future Polish monarch Władysław III Spindleshanks stayed at the local court of Duke Bogusław I in 1186, on behalf of his father, Duke of Greater Poland Mieszko III the Old, who also periodically was the High Duke of Poland. Following a conflict between his heirs and Canute VI of Denmark, the settlement was destroyed in 1189, but the fortress was reconstructed and manned with