The Erkesiya was a 142-kilometer long (88 miles) border wall, or, rather, a border rampart, a fortification combining a moat, earthwork, stone and wood structures which was built by the Ancient Bulgars of the First Bulgarian Empire (632/680 – 1018) in today’s Southeast Bulgaria as a line of defense against the Byzantine Empire.
The Erkesiya (meaning a “large trench" in Greek) ran all the way from the Black Sea coast in the east to the valley of the Maritsa River, and, by extension, the beginning of the Rhodope Mountains, in the west through mostly flat terrain in order to create a defensive barrier for the First Bulgarian Empire against Byzantium (the Eastern Roman Empire).
It was the largest border wall / rampart of the type built by the Ancient Bulgars south of the Danube River, and was part of a whole system of border ramparts established in the border and buffer zones of the First Bulgarian Empire.
In addition to its military and defense functions, the Erkesiya border rampart was also a well-developed customs border which was in use as such up until the Ottoman conquest of the Balkans in the 14th century.
The Erkesiya was longer than the world famous Hadrian’s Wall built in Roman Britain, whose total length was 117.5 km (73 miles) (which figures even more prominently in popular culture now that it has served as the model for the Wall built for stopping the White Walkers in ‘Game of Thrones’ / ‘Song of Ice and Fire’).
The other Ancient Roman border wall in Britain, the Antonine Wall in Scotland, was even shorter: it spanned a total of 63 kilometers (39 miles).
It is said to be still visible from space. Today it runs through the territories of seven Bulgarian municipalities – Burgas, Sredets, Karnobat, Straldzha, Tundzha, Galabovo, and Simeonovgrad.
The construction of the Erkesiya border rampart between the First Bulgarian Empire and Byzantium is believed to have been started as early as 716 AD, during the reign of Khan Tervel (r. 700 – 721), also known as the Rescuer of Europe for defeating a massive force of the Arab Caliphate in the Battle of Constantinople in 718.
In 705, by intervening in a dispute for the Byzantine throne, Tervel gained for Bulgaria its first territories south of the Balkan Mountains (Stara Planina), the so called Zagore or Zagora region. The cession of the said territory by Byzantium and the borderline was confirmed in a 716 treaty between him and Byzantine Emperor Theodosius III (r. 715 – 717). This appears to be the borderline covered by the Erkesiya border rampart.
The same borderline was noted in the first article of the 30-year peace treaty signed 100 years later, in 815, by Bulgarian Khan Omurtag (r. 814 – 831) and Byzantine Emperor Leo V the Armenian (r. 813 – 820).
The 142-km long Erkesiya border rampart of the First Bulgarian Empire can be divided in three sections.
The western section of the Erkesiya is located west of the Tundzha River, and is 64 km (40 miles) long. It is believed to have been built partly between 716 and 755, a rare period without wars between the First Bulgarian Empire and Byzantium, and to have been completed after the bilateral peace treaty of Omurtag and Leo V of 815.
This older, western section of the Erkesiya border rampart is less sizable than the sections between the Tundzha River and the Black Sea.
According to its modern-day measurements, it is 10 meters (33 feet) wide. Its moat is 4 meters (13 feet) wide, and 1 meter (3 feet) depth, its earthwork is 6 meters (20 feet) wide, and 1 meter tall.
The eastern section of the Erkesiya is 67 km (41 miles) long, and ran from the Tundzha River to today’s town of Debelt, the site of the Ancient Roman city of Deultum and the Deultum – Debelt Archaeological Preserve.
This section is 22 meters (72 feet) wide; the moat is 7 meters (23 feet) wide, and 1.5 meters (5 feet) deep; the earthwork is 15 meters (50 feet) wide, and 2 meters (6.5 feet) tall. The eastern section of the Erkesiya was crossed by the most important roads at the time connecting Byzantium’s capital Constantinople with the capitals of the First Bulgarian Empire Pliska and Veliki Preslav in today’s Northeast Bulgaria.
A third section of the Erkesiya border rampart was built between the town of Debelt and the Burgas Lake (Lake Vaya), a liman connected to the Black Sea. This so called “Little Erkesiya" was long 11 km (6.8 miles). The eastern section of the Erkesiya and the Little Erkesiya are believed to have been built after 812 – 813.
According to some researchers, the initiative might have come from Bulgaria’s Khan Krum (r. 803 – 814) after the 811 invasion of the First Bulgarian Empire by Byzantine Emperor Nicephorus I Genicus (r. 802 – 811).
While Nicephorus I’s was ultimately defeated in the Battle of the Varbitsa Pass (also known as the Battle of Pliska), he did ransack the then Bulgarian capital Pliska first. So Khan Krum might have championed the construction of the Erkesiya as an iniatial line of defense to allow enough time of Bulgaria’s troops at the Balkan Mountain passes to prepare for an invasion from the southeast.
In addition to the moat and the earthwork, in building the Erkeisya border wall, the Ancient Bulgars also used stone as well as wooden palisades, and also integrated into it the vegetation by forming hedges.
Researchers’ estimates show that about 13 cubic meters of soil were used for the construction of one meter of the Erkesiya earthwork, and that a total of some 2.6 million cubic meters of soil were dug up and used for the entire border wall. The same estimates also state that if 1 cubic meter of soil could be used by 1 person per in 1 day, that would mean that about 20,000 had to work on the construction of the Erkesiya’s earthwork for a total of 130 days.
The structure and size of the Erkesiya border wall are similar to border walls built by the Ancient Bulgars in the region of Bessarabia in today’s Moldova and Ukraine, and three walls they built in today’s Northwest Bulgaria.
Bulgaria’s Erkesiya border wall was mentioned by Arab author Abu Umar al-Garmi in the mid-9th century, and in the 10th century by Arab historian and geographer Al-Masudi, who wrote that the land of the Bulgarians is fenced off with a thorny hedge which had openings through wooden doors to which he referred as “wooden windows".
According to an account of 9th century Benedictine monk Notker the Stammerer, the Ancient Bulgars built the Erkesiya by first erecting two parallel lines of wooden poles 20 feet away from one another.
The space between the two palisade lines was filled with stone or clay, and they covered that with the soil they had extracting from digging the moat. On top of the earthwork, they planted trees and other vegetation that formed a hedge.
Ancient Bulgar earthwork border walls / rampart usually varied in width from 10 meters (33 feet) to 40 meters (131 feet). Their moat was usually about 3 meters deep (9.8 feet, and the earthwork was about 3-4 meters tall (appr. 10 feet). At some more vulnerable points, palisades were built on top of the earthwork.
The Erkesiya and the other Ancient Bulgarian border walls could be crosses through passages left for the main roads, which were guarded with wooden tower gates equipped with drawbridges for the moat. These border crossing points were described by Arab author Al-Masudi as “wooden windows". They were used as customs offices of the First Bulgarian Empire.
Nowadays, the eastern section of the Erkesiya between Debelt and the Tundzha River is best preserved, while much of the western section and the Little Erkesiya has been leveled.
Archaeological research has proven that the Erkesiya was a military facility thorough most of the period of the First Bulgarian Empire. It was no longer in use following the 10th century. (Bulgaria was conquered by Byzantium in 1018, and was ruled by it until the Uprising of Tsar Petar IV and Tsar Asen I in 1185.
In modern-day Bulgaria, the Erkesiya border wall / rampart enjoys the status of a monument of culture of national importance, which is the highest possible.
The best preserved sections of the Erkesiya, which are also best for visiting, are the one that is part of the Deultum – Debelt Archaeological Preserve, the earthwork camp near the town of Lyulin, and earthwork fortifications at the town of Tenevo, Tundzha Municipality.
The Ancient Bulgar border rampart Erkesiya was marked on maps published as late as the end of the 19th century.
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