Principality of Polotsk
In 1206, the crusaders subdued the Livonian stronghold in Turaida on the right bank of Gauja River, the ancient trading route to the Northwestern Rus. In order to gain control over the left bank of Gauja, the stone castle was built in Sigulda before 1210. By 1211, the Livonian province of Metsepole (now Limbaži district) and the mixed Livonian-Latgallian inhabited county of Idumea (now Straupe) was converted to the Roman Catholic faith. The last battle against the Livonians was the siege of Satezele hillfort near to Sigulda in 1212. The Livonians, who had been paying tribute to the East Slavic Principality of Polotsk, had at first considered the Germans as useful allies. The first prominent Livonian to be christened was their leader Caupo of Turaida. As the German grip tightened, the Livonians rebelled against the crusaders and the christened chief, but were put down. Caupo of Turaida remained an ally of the crusaders until his death in the Battle of St. Matthew's Day in 1217.