Various Anatolian Turkish Beyliks In 1303, the Byzantine Emperor Andronicus II Palaeologus hired 6,500 Catalan mercenaries under Roger de Flor[2] to campaign against the Turks in the spring and summer of the same year.

However, the Byzantines got more than what they bargained for; the mercenaries were difficult to restrain and consequently much of the reconquered territory was laid to waste.

When their leader Roger de Flor was assassinated in Gallipoli on 3 April 1305 by Michael IX Palaeologus followed by a massacre of 1,300 Catalans,[2] the mercenaries began a two-year pillage in revenge and crossed over to Thrace and Macedonia under the command of their new leader, Berenguer d'Entença,[3] where further raiding occurred.

As a result of this brutality, the Company was excommunicated by Pope Clement V.[3] Eventually the Catalan mercenaries claimed the Duchy of Athens for themselves in 1311 and would remain there until 1379,[3] leaving behind a devastated Byzantium.

Thus, the Catalans' campaign was a short-term Byzantine victory, but benefited the Turks in the long term.