Козьма Пражский
Wenceslaus's brother Boleslaus I (r. 935–972) defeated a number of Bohemian dukes who opposed his rule, erected new fortresses all over Bohemia, and conquered significant parts of Moravia, Silesia, and other territories. Cosmas of Prague reports that Boleslaus I "built twenty churches for the Christian religion" in his reign. Churches from the second half of the century have been found at Dobřichov, Plzeň, and other settlements. The earliest churches in Bohemia were wooden constructions. The church dedicated to the Virgin at Prague Castle was the first to have been built of stone. Boleslaus I ordered that markets be held on Sundays in his forts in order to persuade his subjects to attend Sunday Mass. Pope John XIII authorized him to establish two bishoprics in his realm in 962, but Michael, Bishop of Regensburg, prevented the division of his diocese. Cosmas of Prague narrates that the Pope forbade Slavic liturgy in his letter to Boleslaus II, but the credibility of this report has been challenged.