The Byzantine Expulsion was a process by which (mostly Lombard) armies expurged several Slavic tribes from the territories south of the Danube (which they had invaded a few years previous) or to extract from them vows of loyalty to the Byzantine Empire. It was a great success, leading Slavic tribes to flee north into Dacia and the Avar lands, while some Bulgars and other Slavs were allowed to remain in Moesia establishing the vassal Tsardom of Bulgaria. The area not only bought Byzantium enough time so to recover from the defeats in the Middle East but also created several strong Byzantine allies to help defend the land, established Moesia as a place for settlement of mercenaries and other non-Greek elements and establish closer Western-Romanian bounds.