Justinian acquired Tervel's support for an attempted restoration to the Byzantine throne in exchange for friendship, gifts, and his daughter in marriage.

Only three years later, however, when Justinian II consolidated his throne he violated this arrangement and commenced military operations to recover the ceded area but Khan Tervel routed the Byzantines at the Battle of Anchialus (near present-day Pomorie) in 708.

In 711, faced by a serious revolt in Asia Minor, Justinian again sought the aid of Tervel, but obtained only lukewarm support manifested in an army of 3,000.

However, the Byzantine Chronicler Theophanes the Confessor ascribes Tervel a role in an attempt to restore the deposed Emperor Anastasius II in 718 or 719.

If Tervel had survived this long, he would have been the Bulgarian ruler who concluded a new treaty (confirming the annual tribute paid by the Byzantines to Bulgaria, the territorial concessions in Thrace, regulating commercial relations and the treating of political refugees) with Emperor Theodosius III in 716.

However, elsewhere Theophanes records the name of the Bulgarian ruler who concluded the treaty of 716 as Kormesios, i.e., Tervel's eventual successor Kormesiy.

Most researches agree that it was during the time of Tervel when the famous rock relief the Madara Rider was created as a memorial to the victories over the Byzantines, to honour his father Asparukh and as an expression of the glory of the Bulgarian state.

During the summer of the same year the Arabs, led by Maslama ibn Abd al-Malik, crossed the Dardanelles and besieged Constantinople with a large army and navy.

In 719, Tervel again interfered in the internal affairs of the Byzantine Empire when the deposed emperor Anastasios II asked for his assistance to regain the throne.

In his Slav-Bulgarian History (1762), Paisius of Hilendar interprets Tervel's character based on a copperplate engraving from Hristofor Žefarović's Stemmatografia (1741), which depicts St. David, king of Bulgaria and St. Theoctistus.

[6] The interpretations by Paisius, by analogy and without critical analysis, will be taken up in the later Bulgarian literature and will create a fictitious and until then non-existent saint cult, which will be reflected in the paintings of the 18th and 19th centuries.