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 II Lambert name for his son was an expression of warming relations between Bolesław I and his stepmother Oda. He organized two devastating invasions to Saxony in 1028 and 1030. Then Mieszko II ran a defensive war against Germany, Bohemia and the Kievan princes. Mieszko II was forced to escape from the country in 1031 after an attack of Yaroslav I the Wise, who installed Mieszko's older half-brother Bezprym onto the Polish throne. Mieszko took refuge in Bohemia, where he was imprisoned by the Duke Oldrich. In 1032 he regained power in one of the three districts, then united the country, making