Mieszko I
Involvement in German internal disputes; Second marriage

After the death of Emperor Otto I in 973 Mieszko, like his brother-in-law, Duke Boleslaus II of Bohemia, joined the German opposition in support of the attempted imperial succession of Henry II, Duke of Bavaria. Mieszko may have been motivated by revenge because of the (presumably) negative verdict of the Quedlinburg summit, but, more importantly, he may have wanted more favorable terms for his cooperation with Germany. The participation of Mieszko in the conspiracy against Otto II was documented in only one source, the chronicles of the monastery in Altaich in its entry for the year 974. The Duke of Bavaria was defeated, and Emperor Otto II regained full power. Shortly afterwards, the young emperor waged a retaliatory expedition against Bohemia, in 978 forcing Duke Boleslaus into submission.

In 977 Mieszko's wife, Dobrawa, died. At first there were no apparent repercussions, as the Polish ruler had maintained his alliance with Bohemia.

In 979 Otto II supposedly attacked Poland. Mention of this event can be found in the Chronicle of the Bishops of Cambrai from the 11th century. The effects of this expedition are unknown, but it is suspected that the Emperor did not succeed. Due to bad weather, the Emperor was back at the border of Thuringia and Saxony in December of that year. It is uncertain whether the invasion actually took place. The chronicle only stated that it was an expedition "against the Slavs". Archaeological discoveries appear to support the thesis of Otto's invasion. In the last quarter of the 10th century there had been a radical expansion of the fortifications at Gniezno and Ostrów Lednicki, which may be associated with the Polish-German war, or the expectation of such. The duration of the expedition suggests that it may have reached as far east as the vicinity of Poznań.

The Polish-German agreement was concluded in the spring or possibly summer of 980, because in November of that year Otto II left his country and went to Italy. It appears that during this time Mieszko I married Oda, daughter of Dietrich of Haldensleben, Margrave of the Northern March, after abducting her from the monastery of Kalbe. Chronicler Thietmar described the event as follows:

Although Thietmar made no mention of warfare that possibly took place on this occasion, the information on the return of the accord, acting for the good of the country and release of prisoners indicate that a conflict actually did occur.

The marriage with Oda considerably affected the position and prestige of Mieszko, who entered the world of Saxon aristocracy. As a son-in-law of Margrave Dietrich, he gained an ally in one of the most influential politicians of the Holy Roman Empire. As the Margrave was a distant relative of the Emperor, Mieszko became a member of the circle connected to the imperial ruling house.
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