Mieszko II Lambert of Pöhlde asked the Emperor to defend against the attacks of Mieszko II, promising support in the fight against the Polish ruler. Despite the treaty which secured peace between Poland and Germany, the Emperor soon armed a retaliatory expedition against Mieszko II. Conrad II's army arrived to Lusatia in the autumn of 1029 and began the siege of Bautzen; but the German troops did not receive the promised support of the Lutici tribe and the expedition failed. Threatened by the Hungarians, the Emperor was forced to retreat. Probably in this same year the son of Oldřich, Bretislaus I, attacked and
Mieszko I of Poland the Polabian Slavs. On the other hand, the supporters of the Gero's invasion theory believe that the Margrave did actually carry out a successful invasion, as a result of which Mieszko I was forced to pay tribute to the Emperor and also was compelled to adopt Catholicism through the German Church. The thesis that proposes the introduction of Catholicism as a result of this war finds no confirmation in German sources. The homage is then a separate issue, since, according to the chronicle of Thietmar, Mieszko actually paid tribute to the Emperor from the lands "usque in Vurta fluvium" (up