Boleslaus (Boleslav) gained his peculiar nickname for an act of particular brutality. His brother was Wenceslas I (Vaclav). Wenceslas, as the older brother, was the Duke of Bohemia. Boleslaus, at the instigation of their mother, Drahomira, murdered Wenceslas and took the title.
Boleslaus and Wenceslas were the sons of Vratislaus I (Vratislav), who died in battle in the year 921. Their grandparents, Borivoj and Ludmila, were baptized by St. Methodius, who, along with his brother Cyril, popularized Slavic (rather than Latin) Christianity in Bohemia and Moravia. After the death of Vratislaus, Ludmila took charge of caring for and educating Wenceslas, while Drahomira took care of Boleslaus.
Drahomira had been a pagan, and perhaps still was. Some believe that this is the reason she and Ludmila did not get along. Whatever the reason, she and Ludmila (who, upon the death of Vratislaus, was regent of Bohemia) were often at odds. Furthermore, Ludmila was a strong influence on Wenceslas. Drahomira had Ludmila murdered at Tetin Castle, then concentrated on ensuring that Boleslaus, not Wenceslas, would be the Duke of Bohemia.
Boleslaus went along with his mother’s plans to murder his own brother, and he and his henchmen committed the murder in 935. Legend has it that Boleslaus’s son was born at the precise time Wenceslas was murdered. The boy was given the name Strachkvas, which means “dreadful feast”.
In spite of the way Boleslaus gained the dukedom, he proved to be a capable ruler. One of Drahomira’s concerns was that the late Wenceslas had shown too much favor to the Kingdom of the Franks. Wenceslas, having seen the military might of King Henry (also known as Henry the Fowler), felt it wise to pay a yearly tribute to the kingdom. Boleslaus ended this practice. Henry died the year after Wenceslas, but this decision meant a long and brutal war with his son and heir, King Otto the Great.
In 936, Boleslaus defeated two of Otto’s armies. Skirmishes continued for more than a decade, until, in the year 950, Otto attempted to take a castle owned by Boleslaus’s son. Boleslaus then promised to reinstate the tributes to the Kingdom of the Franks. Now allies, the two countries united to defeat the Magyars at the Battle of Lechfeld on August 10, 955. Thanks to this defeat, and other victorious battles, Boleslaus was able to expand the territory of his dukedom significantly. During his reign, he ruled over an area that included Cracow and Lvov, as well as land north of Cracow.
There is some speculation about Boleslaus and religion. According to some sources, Drahomira was successful in influencing him against Christianity. If she was, it did not last. His regret over the murder of his brother led him to have his son Strachkvas educated to join the clergy. His daughter Mlada was a Benedictine abbess. His son Boleslaus II founded the Diocese of Prague, which caused him to receive the nickname of “the Pious” (far better than the name his father bore). And his daughter Doubravka married Mieszko I of Poland and brought Christianity to that country.