Boleslaw, endeavoring to extend his influence to…

Boleslaw, endeavoring to extend his influence to the territory of the Prussians, encourages Christianizing missions in the Prussian lands.

Most famous of these is the mission of Vojtěch from the Bohemian princely Slavník clan, former bishop of Prague.

Known as Adalbert of Prague upon the death of Adalbert of Magdeburg in 981, Adalbert's mission takes place in 997 and ends in the missionary's martyrdom at the hands of the pagan Prussians.

It is a standard procedure of Christian missionaries to attempt to chop down sacred oak trees, which they had done in many other places, including Saxony.

Because the trees are objects of worship and the spirits believed to inhabit the trees are feared for their powers, this is done to demonstrate to the non-Christians that no supernatural powers protect the trees from the Christians.

When the missionaries ignore warnings to stay away from the sacred oak groves, Adalbert is martyred for his supposed sacrilege in April 997 on the Baltic Sea coast east of Truso (a medieval emporia near the modern city of Elbląg), or near Tenkitten and Fischhausen.

The remains of the missionary are held for ransom by the Prussians and Bohemian Přemyslid rulers refuse to pay for Adalbert's body.

Consequently it is purchased by Duke Boleslaw, according to one story, in exchange for its weight in gold, and buried in Gniezno.

A few years later Adalbert will be canonized as Saint Adalbert of Prague.