The siege of Głogów or Defense of Głogów (, ) was fought on 24 August 1109 at the Silesian town of Głogów, between the Kingdom of Poland and the Holy Roman Empire. Recorded by the medieval chronicler Gallus Anonymus, it is one of the most well known battles in Polish history. The Polish forces were led by Duke Bolesław III Wrymouth, while the Imperial forces were under the command of King Henry V of Germany. Bolesław was victorious. Prelude After a long-term rivalry within the ruling Piast dynasty, Bolesław III, in 1107, had finally expelled his elder half-brother and co-ruler Duke Zbigniew from Poland. Zbigniew fled to the Holy Roman Empire where he sought help from King Henry V. The King, however, did not take action as he was stuck in an inner-Hungarian rivalry, supporting the Árpád Prince Álmos against his brother King Coloman, and had started an armed expedition to Bratislava (Pozsony). Henry tangled with Bolesław when the Polish duke, loyal to King Coloman, took the occasion to campaign in the Bohemian lands in 1108: as soon as the Bohemian Duke Svatopluk heard of the invasion, he left the Imperial army to oust the Polish troops. Left alone, King Henry was forced to abandon his Hungarian campaign. Chafing under this defeat, Henry finally associated himself with Zbigniew and requested Bolesław to reinstate his half-brother as co-ruler, as well as to pay an annual tribute to the Empire. The Polish Duke categorically rejected both demands. The next year, the German forces gathered at Erfurt, crossed the Polish border near Krosno on the Bóbr River, and on St. Bartholomew's Day approached the fortified town of Głogów (Svatopluk's troops arrived in September). At first they defeated a Polish garrison which was stationed near the town, while Bolesław rushed from his battle against the Pomeranians at Nakło. Siege According to Gallus' Gesta principum Polonorum, King Henry resorted to lay siege to Głogów but granted its citizens a five-day ceasefire to ask their King for permission to surrender. He allegedly even made the townsmen give up their children as hostages as a guarantee of the ceasefire, and promised to give them back alive no matter what Bolesław's answer would be. The Polish Duke, however, had no intention to hand over the city, and ordered the defense of Głogów. After the five days were up, King Henry began to barrage the town. Breaking his promise,