Battle in Thrace, 538

In 538, a large body of Bulgars led by two chiefs called "kings", Bulgar and Drong, attacked the regions of Scythia Minor and Moesia. They defeated the Byzantine army sent against them under the commander Justin, who died in the battle. The Bulgars then crossed the Balkan Mountains and penetrated Eastern Thrace. There, a large Byzantine army awaited them under the renowned commanders Constantine, Godilas and Acum. 

Some of the Bulgars, together with their two leaders, were surrounded and killed. The remaining Bulgars launched a surprise attack on the Byzantines and captured their commanders with lassos.