 In Antiquity, both Bulgaria and Romania were inhabited by Thracian tribes, contributing to the ethnogenesis of the Romanian people and possibly the Bulgarian people (along with Slavs and Bulgars), although this is a matter of dispute.During the Migration Period, both the Slavs and the Bulgars crossed what is today Romania to settle in the plains south of the Danube, establishing the First Bulgarian Empire in the 7th century.In the Middle Ages, the lands between the Danube and the Carpathians were scarcely settled, but they were often at least nominally under Bulgarian control in the 9th and 10th century, as well as during some periods of the Second Bulgarian Empire.