[1] Markeli acquired its strategic importance in the late 7th century, when the establishment of the First Bulgarian Empire and its expansion turned it into a vital frontier stronghold just south of the Balkan Mountains.

[1] The second battle of Marcellae came during a long period of aggression between Byzantium and Bulgaria, with Bulgarian ruler Kardam and Byzantine Emperor Constantine VI each invading foreign territory in the past few years.

[7] In 811, Nikephoros I Logothetes's forces departed from Markeli in their ill-fated invasion of Bulgaria,[1] which saw the emperor being killed at the hands of the Bulgarians in the Battle of Pliska.

[8][9] Byzantine scholar Anna Komnene writes that in 1089 her father Alexios I Komnenos had conflicts and negotiations with the Pechenegs and Cumans who had pitched their tents at Markeli (Marcellae).

[11] Markeli is situated near the Mochuritsa River (a major tributary of the Tundzha), on the western tip of the Hisar highland, which is part of the southeastern Balkan Mountains.

[11] The fortifications were constructed out of crushed stones with integrated rows of bricks and are thought to date to the reign of either Anastasius I (491–518) or Justinian I (527–565), i.e. the late 5th to mid-6th century.