[1] 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.

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 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).

Breaking his promise, he chained the child hostages to his siege engines, hoping that the people of Głogów would not shoot their own offspring, which would allow him to conquer the Polish settlement.

After centuries-long ambivalent relations with Germany, the successful defense and the tradition of Henry's cruelty had evolved to a key element in the memory of the Polish nation.