The Late Antiquity (Early Byzantine) and medieval Bulgarian fortress of Rusocastro is located in today’s Southeast Bulgaria, close to the Black Sea city of Burgas. In the 2nd millennium BC the Ancient Thracians set up a cult sanctuary of the Sun God, the Mother Goddess, and the Thracian Horseman, also known as god Heros, near the legendary cave known today as Rusina Cave or Rusa’s Hole. Its site was settled in the period of Ancient Thrace, and was an important center in the Thracians’ Odrysian Kingdom. However, the fortress itself was built in the 5th century AD on a strategically located hill.
The Early Byzantine fortress was most probably destroyed in the Slavic and Avar invasions in the 7th century. The Rusocastro Fortress was rebuilt by the Bulgarians in the 9th century, during the First Bulgarian Empire (632/680 – 1018 AD), at the time of the construction of the Bulgarian border rampart known as Erkesiya (in use in the 10th-11th century), and was a major stronghold in the geographic region of Thrace during the High Middle Ages. The earliest written information about it comes from a 6th century epigraphic monument dedicated to Byzantine military commander Justin, who, according to some Bulgarian scholars, was the great-grandson of Byzantine Emperor Justin I (r. 518-527 AD), the uncle of Emperor Justinian I (r. 527-565 AD). The name Rusocastro was first used in the 12th century by Arab geographer El Idrisi in his work “Geography of the World", where Rusocastro is described as a large and crowded city. The fortress was also mentioned in a number of Byzantine sources from the 14th century relevant to current events.
The Rusocastro Fortress is famous in Bulgarian history for the Rusocastro Battle in which the army of Bulgarian Tsar Ivan Alexander (r. 1331-1371 AD), ruler of the Second Bulgarian Empire (1185-1396 AD), defeated the forces of Byzantine Emperor Andronikos III Palaiologos (Andronicus III Palaeologus) (r. 1328-1341 AD) in 1332 AD. Tsar Ivan Alexander’s victory at Rusocastro is considered the last major military victory of the Bulgarian Empire before its decline in the second half of the 14th century, and its conquest by the Ottoman Turks that ushered in the darkest page in Bulgaria’s history, the Ottoman yoke (1396-1878/1912).
The Rusocastro Fortress was destroyed in Ottoman campaigns in 1443. It has been excavated by archaeologists Milen Nikolov and Dr. Tsanya Drazheva from the Burgas Regional Museum of History. The Bulgarian archaeologists have excavated several churches there including a monastery called St. George, which existed in the 11th-14th century. Unfortunately, a Christian necropolis in the Rusocastro Fortress was partly destroyed in the largest military drills dubbed “Shield" of the countries from the former Soviet-dominated Warsaw Pact that took place in Eastern Bulgaria in 1982.