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, Duke of Cieszyn was on 1 January 1290. In internal politics he pursued vigorous policies. Mieszko carried out intensive colonizing policies and founded many settlements. He also gave city rights to several towns: Cieszyn, Oświęcim (in 1291), Bielsko, Skoczów and Fryštát. On 10 November 1292 he granted the city rights to Zator. Mieszko refused to support any of the Piast pretenders to the Polish throne (Henry IV Probus, Przemysł II and Władysław I the Elbow-high). Instead he stood alongside King Wenceslaus II of Bohemia. On 17 January 1291 the formal agreement was signed in Olomouc which formed the alliance between the Bohemian Kingdom,