Öz Beg was engaged in wars with Bulgaria and the Byzantine Empire from 1320 to 1332. He repeatedly raided Thrace, partly in service of Bulgaria's war against both Byzantium and Serbia that began in 1319. His armies pillaged Thrace for 40 days in 1324 and for 15 days in 1337, taking 300,000 captives. After Öz Beg's death in 1341, his successors did not continue his aggressive policy and contact with Bulgaria lapsed. His attempt to reassert Mongol control over Serbia was unsuccessful in 1330. Byzantine Emperor Andronikos III purportedly gave his illegitimate daughter in marriage to Öz Beg but relations turned sour at the end of Andonikos's reign, and the Mongols mounted raids on Thrace between 1320 and 1324 until the Byzantine port of Vicina Macaria was occupied by the Mongols. Andonikos's daughter, who adopted the name Bayalun, managed to escape back to the Byzantine Empire, apparently fearing her forced conversion to Islam. In the south-east of the Kingdom of Hungary, Wallachia and its ruler Basarab I became an independent power with the support of Öz Beg after 1324.