Already in the 12th century a major trade route developed between northern Germany, the port of Lubeck, through Visby on the island of Gotland, to the mouths of the rivers Dzwina and Narew. Control over that route was bitterly contested between Germany and Denmark. Toward the end of the 12th century the monk Meinhard of Segeberg worked as a missionary of the lower Dzwina and founded there the first German settlement of Ueskull. He was followed by the missionary Bishop Albert Buxhoevden, at the head of a fleet of twenty-three ships. In 1201 he founded at the mouth of the Dzwina the city of Riga, which handled trade with lands extended as far as the Black Sea. Albert had the support of Pope Innocent III, who authorized in 1204 the German order of the Knights of the Sword to conquer and convert the region now known as Latvia and Estonia.
Denmark challenged at first the German expansion in the eastern Baltic. Its king, Waldemar the Victorious, won in 1219 a battle against the Esta and founded the city of Reval. According to legend a Danish flag -- red with a white cross -- dropped from the sky during that battle. But the Germans eventually prevailed, taking Dorpat, Narva, and the island of Ozilia.
The Germans, as we see, took an early interest in the Baltic countries and started their systematic conquest. According to the standards of that period, their action was legally justified, since the Balts and the Ests were still pagans, as were the Prussians, Poland's neighbors.