Excerpts from Books and Wikipedia
"As part of his strategy to keep them permanently away, Henry planned to turn the little dukedom on his eastern flank into a vassal state that would act as a buffer between Germany and another Magyar advance. The dukedom was called Bohemia . . . The new duke of Bohemia was a young man named Wenceslaus, who was a Christian and enthusiastic about an alliance with the powerful German king. . . . Led by Wenceslaus's younger brother Boleslav, this faction insisted that Wenceslaus break the alliance and give up Christianity as well, all in the name of a strong and autonomous Bohemia.
But Wenceslaus refused. In 935, he came to church in the predawn dark for an early mass; Boleslav and the dissident officials met him at the church's door and stabbed him to death." [Bauer: Medieval World, p. 495-6]