Kan Boris Bulgar

Bulgar, or Boris, also known as the Supreme Kan of the Bulgars, ruled from 521/525 to 541. Although his name was replaced by the ethnonym, he was probably succeeded by the powerful Zabergan, who established diplomatic relations with Sasanian Persia and maintained contact with the wife of the Byzantine emperor Justinian I. Genealogically, Bulgar, or Boris, was connected with Irnik, or Eran, and one of these lines is associated with a supposed father or grandfather of Zabergan.

In 538, Bulgar and Kan Drong advanced south of the Danube, initially into Dobrudja, where he defeated the commander Justin and established himself in the area of Dorostol, now Silistra. This battle formed part of a series of military operations between Bulgaria and the Byzantine Empire linked to the Persian–Byzantine War of 540–561, when Khosrow I was the Sasanian shah.

Bulgar was the first kan known by the ethnonym 'Bulgar' and was well known among Byzantine chroniclers and politicians for his bold advance south of the Balkan Mountains, which provoked even Emperor Justinian I. He may also have appeared in the 10th-century history of Joseph Genesios, who connects the lineage of Tsar Boris I Michael and Kan Krum with Bulgar.