imperial forces crossed the river Oder, Bolesław sent a detachment of Moravian knights in a diversionary attack against the Eastern March of the empire. Soon after, the imperial army, having suffered a defeat near the Bóbr marshes, retreated from Poland without any permanent gains. After this event, Bolesław's forces took the initiative. Margrave Gero II of Meissen was defeated and killed during a clash with the Polish forces in late 1015. In 1015 and 1017, Bolesław I attacked the Eastern March and was defeated twice by Henry the Strong and his forces. Later that year, Bolesław's son Mieszko was sent to plunder Meissen. His attempt at conquering the city, however, failed. In 1017, Bolesław defeated Duke Henry V of Bavaria. In that same year, supported by his Slavic allies, Emperor Henry once again invaded Poland, albeit once again to very little effect. He did besiege the cities of Głogów and Niemcza, but was unable to conquer them. The imperial forces once again were forced to retreat, suffering significant losses. Taking advantage of the involvement of Czech troops, Bolesław ordered his son to invade Bohemia, where Mieszko met very little resistance. On 30 January 1018, the Peace of Bautzen was signed. The Polish ruler was able to keep the contested marches of Lusatia and Sorbian Meissen not as fiefs, but as a part of Polish territory, and also received military aid in his expedition against Rus'. Also, Bolesław (then a widower) strengthened his dynastic bonds with the German nobility through his marriage with Oda, daughter of Margrave Eckard I of Meissen. The wedding took place four days later, on 3 February in the castle of Cziczani (also Sciciani, at the site of either modern Groß-Seitschen or Zützen). War in Kiev (1018) Bolesław organised his first expedition east, to support his son-in-law Sviatopolk I of Kiev, in 1013, but the decisive engagements were to take place in 1018 after the Peace of Bautzen was already signed. At the request of Sviatopolk I, in what became known as the Kiev Expedition of 1018, the Polish duke sent an expedition to Kievan Rus' with an army of 2,000–5,000 Polish warriors, in addition to Thietmar's reported 1,000 Pechenegs, 300 German knights, and 500 Hungarian mercenaries. After collecting his forces during June, Bolesław led his troops to the border in July and on 23 July at the banks of the Bug River, near Wołyń, he defeated