Around 924-5, he became Duke in his own right and gathered the nobles who were Christians to depose his mother. This did not make all well in Bohemia, however, since there were still plenty of pagan nobles who did not appreciate the religion of their ruler. Wenceslaus' younger brother, Boleslav, was pagan, and some of the nobles tried to create a faction around him, hoping to replace Wenceslaus.
But Wenceslaus had plenty of external political difficulties as well. Henry I, the Christian King of Germany, attacked Bohemia with help from Duke Arnulf of Bavaria. The probably reason is that Henry I needed a tribute from Bohemia that had first been established in 895 and had recently been stopped. Henry himself owed tribute to the Magyars, and Germany very likely needed the money it could get from Bohemia in order to make his own payments.* Rather than engage in a war, Wenceslaus swore fealty to Henry and made the payment. The nobles—especially the pagan nobles—would not have appreciated becoming subservient to another country, especially a Christian one.
|Wenceslaus, pursued, tries to enter church|
A cult venerating him built up immediately after his death. The hagiographies written about him stressed how he would give alms to poor people. Whether this were true did not matter years later when it became celebrated as fact. Although he had only been a duke, the Holy Roman Emperor Otto I proclaimed him a King, hence the title given in the holiday song. (There was an actual King Wenceslaus of Bohemia, but that was 300 years after the saint.)
His reign was short, and we cannot confirm the piety attributed to him. His legend became very powerful, however, enough to have him proclaimed the patron saint of Czechoslovakia. His feast day is the day of his death, 28 September, but he will forever be associated with 26 December, the Feast of St. Stephen, because of the 1853 song written by the English priest and scholar, John Mason Neale.
And just for the sake of completion.
*The politics of this situation were complicated, and might need their own post to clarify.