mother's uncle Duke Wenceslaus I of Bohemia as the patron saint of Poland. Bolesław sent reinforcements to the Holy Roman Empire to fight against the Polabian Slavs in summer 992. Bolesław personally led a Polish army to assist the imperial troops in invading the land of the Abodrites or Veleti in 995. During the campaign, he met the young German monarch, Otto III. Soběslav, the head of the Bohemian Slavník dynasty, also participated in the 995 campaign. Taking advantage of Soběslav's absence, Boleslav II of Bohemia invaded the Slavníks' domains and had most members of the family murdered. After learning of his kinsmen's fate, Soběslav settled in Poland. Bolesław gave shelter to him "for the sake of [Soběslav's] holy brother", Bishop Adalbert of Prague, according to the latter's hagiographies. Adalbert (known as Wojciech before his consecration) also came to Poland in 996, because Bolesław "was quite amicably disposed towards him". Adalbert's hagiographies suggest that the bishop and Bolesław closely cooperated. In early 997 Adalbert left Poland to proselytise among the Prussians, who had been invading the eastern borderlands of Bolesław's realm. However, the pagans murdered him on 23 April 997. Bolesław ransomed Adalbert's remains, paying its weight in gold, and buried it in Gniezno. He sent parts of the martyr bishop's corpse to Emperor Otto III who had been Adalbert's friend. Congress of Gniezno and its aftermath (999–1002) Emperor Otto III held a synod in Rome where Adalbert was canonised on the emperor's request on 29 June 999. Before 2 December 999, Adalbert's brother, Radim Gaudentius, was consecrated "Saint Adalbert's archbishop". Otto III made a pilgrimage to Saint Adalbert's tomb in Gniezno, accompanied by Pope Sylvester II's legate, Robert, in early 1000. Thietmar of Merseburg mentioned that it "would be impossible to believe or describe" how Bolesław received the emperor and conducted him to Gniezno. A century later, Gallus Anonymus added that "[m]arvelous and wonderful sights Bolesław set before the emperor when he arrived: the ranks first of the knights in all their variety, and then of the princes, lined up on a spacious plain like choirs, each separate unit set apart by the distinct and varied colors of its apparel, and no garment there was of inferior quality, but of the most precious stuff that might anywhere be found." Bolesław took advantage of the emperor's pilgrimage. After the Emperor's visit in Gniezno, Poland started to develop into a sovereign