Congress of Gniezno

After his death in 997 during a mission among the pagan Prussian tribes, Bishop Adalbert of Prague was quickly canonized by the common effort of Duke Bolesław I and Emperor Otto III.

[1] His body, bought back by Bolesław from the Prussians for its weight in gold, was put into a tomb at Gniezno Cathedral, which became the ecclesiastical center of Poland.

According to the chronicles of Thietmar of Merseburg, Otto III, who had been a friend and pupil of Adalbert,[1] committed to a pilgrimage from Italy to St. Adalbert's tomb in Gniezno; in his attempt to extend the influence of Christianity in Central and Eastern Europe, and to renew the Holy Roman Empire based on a federal concept ("renovatio imperii Romanorum") with the Polish and Hungarian duchies upgraded to eastern federati of the empire.

The Polish Piast dynasty under Mieszko I had extended their domains beyond the Oder river, where their claims to power collided with the interests of the Saxon margrave Gero.

After his defeat by Gero's troops in 963, Mieszko I decided to come to terms with Emperor Otto I and agreed to pay tribute for this part of his lands.

As a precaution however, shortly before his death in 992 he placed his realm (Civitas Schinesghe) under the protection of Pope John XV according to the dagome iudex regest.

Between the 7th and 15th of March Otto invested Bolesław with the titles frater et cooperator Imperii ("Brother and Partner of the Empire") and populi Romani amicus et socius[2] as rendered in the 1115 Gesta principum Polonorum by the Kraków chronicler Gallus Anonymus, the first author of Polish history.

As a consequence, the excellent relations between the Empire and Poland marked by the Congress of Gniezno turned into a state of hostility that soon emerged into a German–Polish War which finally ended with the 1018 Peace of Bautzen.