The Duchy of Estonia was a Danish dominion which existed in the Baltic nation of Estonia from 1219 to 1346, with Reval (Tallinn) serving as its capital. During the 1218 Livonian Crusade, Pope Honorius III gave King Valdemar II of Denmark a free hand to conquer Estonia from the pagan Livonians, and the Danes won a great victory over the native Estonians at the Battle of Lyndanisse in 1219, conquering Estonia and adopting the Dannebrog as their national flag. In 1220, the Danes gave up their claim on southern Livonia to the Sword Brethren, but, in 1227, the Sword Brethren conquered northern Estonia from Denmark. In 1238, following the Battle of Saule, the Brethren were forced to return northern Estonia to Denmark. Starting in 1269, the title "Duke of Estonia" became an ancillary title for the Kings of Denmark. The Danish-founded capital of Reval became a member of the Hanseatic League, and King Valdemar also created a bishopric there. The Kings of Denmark used Danish or Estonian viceroys to govern the duchy from the 1240s onwards, and the Danish army rarely visited the duchy. In 1268 and 1270, the Danes defended Reval against the Lithuanians and Novgorodians, but Christopher II of Denmark's death in 1332 precipitated a political crisis in Estonia. The Estonian government was divided into pro-Danish and pro-German factions, and, after an Estonian revolt against the Danes in 1343, the Teutonic Order occupied Harria. Reval and Wesenberg were betrayed to the Order in 1343, followed by Narva in 1345, and, in 1346, King Valdemar III of Denmark agreed to sell Estonia to the Teutonic Order for 19,000 marks.