Of these mixed lands, the two in which Bohemia was most interested, were the district of Lusatia (afterwards called the Lausitz), over which she disputed with Saxony, and the even more variously peopled province of Silesia, which was the great cause of controversy between Bohemia and Poland. Of these two subjects of difference the Silesian question was the far more pressing and important. The common feeling of danger, produced by Hungarian invasion, had, indeed, affected Poland as much as other European countries; but, as the raids of the invaders grew less frequent, the sense of union, developed by that danger, grew weaker; and when the Hungarians began to settle down as a peaceable and Christian nation, the Poles began to abandon their defensive attitude, and gradually to become aggressive in their turn.
Nor was the Silesian question the only cause of jealousy between Poland and Bohemia. The town of Cracow, the former capital of Croatia, was as much desired by both the rival nations as Silesia could be; since it was important both for military and political purposes. Moreover those ecclesiastical considerations, which were always influencing the foreign politics of Bohemia, played a somewhat important part in the struggle with Poland. The desire of the Polish Duke to secure the burial of Adalbert at Gnesen had not been wholly due to religious feelings. The kings and bishops of Poland wished to make Gnesen the centre of a large diocese, in which Prague should hold a subordinate position; and an offer of money which the Duke of Poland made to a Bohemian monastery founded by Adalbert, was no doubt intended as a bribe to the monks, to induce them to further these schemes of ecclesiastical and political ambition. These enterprises were unfortunately aided by that treacherous family, the Vrs̆ovici, who had already played so fatal a part in their country’s history. They seem to have again tried to carry out their treasons by stirring up family jealousy. Young Boleslav, a nephew of Boleslav the Pious, showed himself eager to assert his claims to the Dukedom of Bohemia. Mĕs̆ek of Poland encouraged his kinsman’s intrigues, and, by a sudden surprise, Cracow was seized, and Silesia was overrun by the Polish troops.