▁became ▁widely ▁used ▁throughout ▁Lower ▁S iles ia ▁and ▁some ▁Upper ▁S iles ian ▁cities . ▁However , ▁after ▁the ▁era ▁of ▁German ▁colon ization , ▁the ▁Polish ▁language ▁was ▁still ▁pre domin ant ▁in ▁Upper ▁S iles ia ▁and ▁parts ▁of ▁Lower ▁and ▁Middle ▁S iles ia ▁north ▁of ▁the ▁Od ra ▁river . ▁Germ ans ▁usually ▁domin ated ▁large ▁cities , ▁and ▁Pol es ▁mostly ▁lived ▁in ▁rural ▁areas . ▁This ▁required ▁the ▁Pr uss ian ▁authorities ▁to ▁issue ▁official ▁documents ▁in ▁Polish , ▁or ▁in ▁German ▁and ▁Polish . ▁The ▁Polish - spe aking ▁territ ories ▁of ▁Lower ▁and ▁Middle ▁S iles ia , ▁commonly ▁called ▁the ▁Polish ▁side ▁until ▁the ▁end ▁of ▁the ▁ 1 9 th ▁century , ▁were ▁mostly ▁German ized ▁in ▁the ▁ 1 8 th ▁and ▁ 1 9 th ▁centuries , ▁except ▁for ▁some ▁areas ▁along ▁the ▁n ort he astern ▁front ier . ▁ ▁Modern ▁history ▁In ▁ 1 7 4 2 , ▁most ▁of ▁S iles ia ▁was ▁seized ▁in ▁the ▁War ▁of ▁the ▁Aust rian ▁Su cc ession ▁by ▁King ▁Frederick ▁the ▁Great ▁of ▁Pr uss ia , ▁who ▁named ▁himself ▁a ▁' Pi ast ▁prince ' ▁( he ▁was ▁actually ▁a ▁remote ▁desc endant ) ▁in ▁his ▁first ▁declaration . ▁The ▁remainder ▁of ▁S iles ia , ▁known ▁as ▁C iesz yn ▁S iles ia , ▁remained ▁in ▁the ▁Aust rian ▁Empire . ▁The ▁Pr uss ian ▁part ▁of ▁S iles ia ▁constit uted ▁the ▁Province ▁of ▁S iles ia