In early 1049, the Byzantine emperor Constantine IX Monomachos decided to transfer 15,000 Pecheneg warriors from their positions in the Balkans to the eastern front.
Upon approaching the Bosporus, however, they decided to turn back, and slowly marched through Bulgaria until they reached the Byzantine city of Serdica.
The local doux (military commander) engaged the Pechenegs in battle, but was soundly defeated.
[1] Constantine soon brought his eastern armies to the west, but they, under the command of Kekaumenos and Hervé Frankopoulos, were soundly defeated.
He organized the formation of multiple counter-guerrilla units, largely made up of Varangians, Franks, and other Westerners, in order to counter the Pechenegs with their own tactics.