Mieszko I of Poland and half a century later, by Bishop Thietmar of Merseburg. By the time Mieszko I took over from his father, the Polans' tribal federation of Greater Poland had for some time been actively expanding. Continuing this process, perhaps in the first years of Mieszko's reign, if it had not been done already by his father, Mieszko I conquered Masovia. Likely also during that period or earlier, at least partially Gdańsk Pomerania was obtained. Mieszko's interests were then concentrated mainly on areas occupied by the eastern (near the Oder River) branches of the Polabian Slavs; some of them became soon subordinated
Mieszko I of Poland the normalization of relations with the Holy Roman Empire and Bohemia, Mieszko I returned to his plans of conquest of the more western part of Pomerania. On 21 September 967 the Polish-Bohemian troops prevailed in the decisive battle against the Wolinians led by Wichmann the Younger, which gave Mieszko the control over the mouth of the Odra River. The German margraves had not opposed Mieszko's activities in Pomerania, perhaps even supported them; the death of the rebellious Wichmann, who succumbed to his wounds soon after the battle, may have been in line with their interests. A telling incident took place