['< sod > at the same time when the [ [ kingdom of germany ] ] grew out of the german [ [ stem duchy | stem duchies ] ] of [ [ east francia ] ] in the 10th century, the west slavic [ [ polans ( western ) | polan ] ] tribes under the [ [ piast dynasty | piast ] ] prince [ [ mieszko i of poland | mieszko i ] ] about 960 were able to establish a sovereign state around [ [ poznan ] ] and [ [ gniezno ] ] in an area later called [ [ greater poland ] ]. mieszko significantly enlarged his territory by conquering [ [ masovia ] ] beyond the [ [ vistula ] ] river, the [ [ silesia ] ] n in 962 / 63 he first met with the [ [ duchy of saxony | saxon ] ] forces of margrave [ [ gero ] ], ruler of the\'\' [ [ marca geronis ] ]\'\' between the [ [ saale ] ] and [ [ bobr ] ] rivers established in 937 by king [ [ otto i, holy roman emperor | otto i of germany ] ]. gero defeated mieszko i in 963 and forced him to recognize otto i as his overlord. < ref > [ [ timothy reuter | reuter ] ], 164. howorth, 226. < / ref > in return for submitting tribute to the newly crowned emperor, otto i granted mieszko i the title of\'\' amicus imperatoris\'\' ( " friend of the emperor " ) and acknowledged his position as\'\' dux poloniae\'\' ( " duke of poland " ). as he could not prevail against gero, mieszko i resorted to consolidate his realm : he strengthened the relations with the bohemian duke [ [ boleslaus i, duke of bohemia | boleslaus i ] ] by marrying his daughter [ [ dobrawa of bohemia | dobrawa ] ] and converted to [ [ christianity ] ] in 966. the next year however, he once again entangled with the troops of the saxon renegade [ [ wichmann the younger ] ], fighting over the island of [ [ wolin ] ] on the [ [ baltic sea | baltic ] ] coast. however he also had to defend the polish border on the lower [ [ oder ] ] river against the forces of margrave [ [ odo i, margrave of the saxon ostmark | odo i of lusatia ] ] at the 972 [ [ battle of cedynia ] ]. < eod > < sod > in the 10th century, the west slavic [ [ polans ( western ) | polan ] ] tribes under the [ [ piast dynasty | piast ] ] prince [ [ mieszko i of poland | mieszko i ] ] about 960 were able to establish a sovereign state around [ [ poznan ] ] and [ [ gniezno ] ] in an area later called [ [ greater poland ] ]. mieszko\'s territory included [ [ masovia ] ] beyond the [ [ vistula ] ] river, [ [ silesia ] ] and in 962 / 63 he first met with the [ [ duchy of saxony | saxon ] ] forces of margrave [ [ gero ] ], ruler of the\'\' [ [ marca geronis ] ]\'\' between the [ [ saale ] ] and [ [ bobr ] ] rivers established in 937 by king [ [ otto i, holy roman emperor | otto i of germany ] ]. during the fight with germanic duchies mieszko i in 963 recognized otto i as emperor < ref > [ [ timothy reuter | reuter ] ], 164. howorth, 226. < / ref > in return for tribute to the newly crowned emperor, otto i reckognized mieszko i as\'\' amicus imperatoris\'\' ( " friend of the emperor " ) and stated that he is\'\' dux poloniae\'\' ( " duke of poland " ). as he could not prevail against gero, mieszko i resorted to consolidate his realm : he strengthened the relations with the bohemian duke [ [ boleslaus i, duke of bohemia | boleslaus i ] ] by marrying his daughter [ [ dobrawa of bohemia | dobrawa ] ] and converted to [ [ christianity ] ] in 966. the next year however, he once again entangled with the troops of the saxon renegade [ [ wichmann the younger ] ], fighting over the island of [ [ wolin ] ] on the [ [ baltic sea | baltic ] ] coast. he also had to defend the polish border on the lower [ [ oder ] ] river against the forces of margrave [ [ odo i, margrave of the saxon ostmark | odo i of lusatia ] ] at the 972 [ [ battle of cedynia ] ]. < eod >']