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Limes Tripolitanus

The fort at Bu Njem in modern Libya. Photo Marco Prins.
The fort at Bu Njem in modern Libya
Limes Tripolitanus: frontier zone of the Roman empire in the west of what is now called Libya. It is interesting because it was not a just a defense line, but is also an example of human intervention in the ecosystem.
'The Garamantes arrived. They bring four donkeys and two Egyptians with letters to you, Gtasazeihemus Opter, and a runaway slave.'
This memo was written in the first half of the third century in Fort Gholaia, a Roman outpost on the empire's southern front. It belongs to a collection of more than 146 notes written on sherds that have survived the centuries. They enable us to catch a glimpse of everyday life in the fort. We read about soldiers on leave, about people who are ill, and about men sent to a police station where travelers feed and water their dromedaries. We read about the arrival of fifty-four recruits, about the return of a soldier who has been on duty during a gladiatorial show, and about soldiers cutting wood for the heating of the fort's bathhouse., the online home of Ancient Warfare magazine
A relief of a peasant with a dromedary. Museum of Bani Walid (Libya). Photo Marco Prins.
A dromedary on a relief from the Bani Walid museum

This last detail will surprise modern visitors of the ruin of Gholaia, near Bu Njem, because it is situated in the desert. The only wood in the neighborhood can be found in the palm grove in the nearby oasis, where cutting trees would be economical suicide. That the soldiers at Bu Njem were able to get wood, proves that in the third century, the country was greener and more fertile than today. The history of the Roman Sahara frontier is, therefore, in the first place a story about human interference with the ecological system.

Nomads and peasants

Tripolitana, 'Land of Three Cities', is the country of the originally Phoenician cities of Sabratha, Oea, and Lepcis Magna. At the beginning of our era, it looked a lot like today: arid but fertile and suitable for the cultivation of olives and cereals. In the interior, Libyan nomads roamed through the Gebel as-Soda and the predesert. In the winter and spring, they traveled from oasis to oasis, but at the end of the summer, they transferred their herds to the Chott al-Djerid area (in Tunisia) and the Tripolitana, where they worked as wage workers on farms, gathering olives. Their dromedaries were used to plow and the manure was quite useful too.

There was some trade as well. Dairy products and meat were bartered for cereals and oil. Ivory, gold, and other articles from Sub-Saharan Africa were exchanged with the products of the urban artisans. There was also some exchange of knowledge. The stories that were told in the Mediterranean ports about the golden apples of the Hesperides contain information about the female warriors who guarded the gold of the Senegal river.

The Limes Tripolitanus. Design Jona Lendering.
The Limes Tripolitanus

Initially, the Roman conquest had no impact upon the interaction between the town dwellers and the desert nomads. Of course, expeditions were conducted in the interior, but this was merely to show the Roman weapons to the tribesmen and to discover where they were living in the spring. The topographer Strabo (c.62 BCE - c.24 CE) knew that the country was "like a leopard's skin, spotted with inhabited places (which the Egyptians call "oases") that are surrounded by waterless and desert land" (Geography, 2.5.33).

The nomads posed no serious military threat. After all, their life style depended upon cooperation with the farmers. But tensions were inevitable and when things went wrong (e.g., during the reign of Tiberius), the tribal warriors could strike swiftly and on many places, because their dromedaries moved faster than anything else. The Romans answered with the construction of police stations, to get early warnings, and roads to reinforce villages if they were attacked. An additional benefit was that new agricultural zones were opened up. Land that had been too far from the urban markets, and had been used as pasture for goats and dromedaries, was now converted into arable land; because of the roads, the products could be sold in the cities. In this way, the region surrounding the Chott al-Djerid was developed in the first century.

As a corollary, the nomads had less space. They now had three options:
  1. They could avoid the north, which meant that they were cut off from the urban markets, and would suffer a very serious setback in living standard.
  2. They could settle and become peasants themselves, which meant that they would lose the freedom to roam across the borderless desert, and -more importantly- would loose contact with their relatives.
  3. They could try to reconquer their pasture.
Those who preferred the second option, helped to intensify the problem for their former fellow-tribesmen, who were again witness to the conversion of a valuable piece of pasture into arable. Those who opted for violence, did not really help to solve the problem either, because the men of the Third legion Augusta retaliated with even more violence, the construction of fortifications and new roads, which opened new zones for agriculture.

The first of the new forts was built at Thiges, with the aim of protecting the peasants around the Chott al-Djerid against nomads of the Gaetulian tribes. This appears to have happened during the reign of Vespasian (69-79), who had been governor of Africa and knew the situation. Under Hadrian (117-138), who visited Africa in 123, the Phazanian nomads were ejected from the area south of modern Gabès and fort Tillibari was built near modern Remada. Only the Tripolitana remained open and underprotected. There was no reason to build fortifications, because the Garamantes lived far away and development of this arid zone was more difficult.

Septimius Severus

It is easy to overestimate the military threat to the Empire's southern boundaries. One single legion, III Augusta, was capable of protecting a frontier zone of 2,500 km: rather less than the four legions that protected the 675 km of the Neckar- Rhine frontier between Schwäbisch Gmünd-Schirenhof and Katwijk. Nevertheless, nomadic incursions ought to be punished and the Roman government had to protect Tripolitana. In 201, soldiers of the Third started to build forts in the oases of Ghadames, Gheriat el-Garbia, and Bu Njem.

Bust of Septimius Severus. Archaeological Museum, Thessaloniki (Greece). Photo Marco Prins.
Septimius Severus (Archaeological Museum, Thessaloniki)

This was more or less sufficient. Of course, potential Garamantian attackers could pass along the fortified oases, but they would inevitably run out of water, because even dromedaries need to drink after about four, five days. This problem could be solved by taking bags of water on the dromedaries, but this made the attackers slower.

Early in 202, the emperor came to visit the frontier. Lucius Septimius Severus was born in Lepcis Magna and and had been in charge of the Mediterranean Empire for almost ten years. His visit to his native country is poorly documented, but the Historia Augusta tells that 'he freed the Tripolitana, the region of his birth, from fear of attack by crushing sundry warlike tribes' (Severus, 18.3). Little is known about the desert war that appears to be implied, but it must have taken place. Severus had already waged war beyond the Euphrates and was to wage war north of the Antonine Wall, so a war beyond the imperial frontier in the Sahara is not impossible, perhaps even likely. However this may be, an expedition against a potential enemy to inspire fear fits within Rome's grand strategy.

To secure the lines of communication, smaller forts and watchtowers were added to the three forts. The most spectacular improvement, however, was the development of the predesert between the three oases and the countryside of Sabratha, Oea, and Lepcis Magna.

Dams, sluices, cisterns

For agriculture, an annual rainfall of about 200 mm is necessary. This type of agriculture is possible along the Libyan coast. If there's not enough rain, access to a lake or a river will help, even when it is not a perennial stream. For example, the Euphrates flows down from the mountains of Armenia, passing through arid Iraq, which becomes extremely fertile. Because the river floods take place when the cereals are on the fields, canals are dug to lead the excessive waters away. In Libya, the Romans decided to improve the Tripolitanan economy by making similar investments in the water management. The difference was, of course, that the project's aim was not to lead water away, but to keep every precious single drop that fell down from heaven.

It is likely that Septimius Severus took initiative. Earlier improvements of the limes Tripolitanus, as it is called, had also needed personal intervention by the emperor. It is even possible that Severus realized the potential when he was in Babylonia fighting against the Parthians. However, it is probable that every Tripolitanan farmer knew what was possible, and in that case, Severus at least has to be credited with earmarking the necessary money. In advance of the expected economical boost, Severus added free olive oil to the system of food supply of Rome (annona) and gave Lepcis Magna a magnificent center. However, not everybody was convinced of the wisdom of these decisions. The historian Cassius Dio, who was the provincial governor of Africa in 223, believed that money had been wasted (Roman History, 77.16.3).

He was wrong. Retired legionaries received plots of land along the wadis, in the arid areas between the oases and the countryside of the three cities. Other settlers were nomads, who continued to pick up sedentary lives. From 220 on there were also immigrants from Syria. The Third legion Gallica had been disbanded by the emperor Heliogabalus, and the legionaries were added to III Augusta. In this way, the Tripolitana became an ethnic melting pot. A name like Julius Mashalul ben Chyrdidry, which has a Latin, Semitic, and a Libyan element, is not exceptional. The soldiers in Bu Njem venerated the Roman god Jupiter together with the Libyan Cannaphar and Ammon. The garrison commander mentioned at the beginning of this article, Gtasazeihemus Opter, has a mixed Semitic-Latin name.

Julius Mashalul ben Chyrdidry lived near Ghirza, a boom town, where the dams and cisterns are still visible, just like the boundaries of the square fields that the Roman surveyors have measured out. One can also see the mausoleums of the people: a strange mix of classical architecture and native-style representations of agricultural activities and fish.

The investments must have been considerable and betray the emperor's support. For example, the doors of the sluices were made of oak wood that must have been imported from the Atlas Mountains, Sicily, or the Cyrenaica. But the returns were also considerable. The peasants cultivated cereals, dates, figs, olives, pod, vegetables. Goats, dromedaries, and a cow or two are also attested. That there was some tree farming can be deduced from the Roman bathhouses, like the one at Bu Njem.

Fifteen years after Dio's negative judgment, the vitality of the new agricultural zone was tested. In 238, governor Gordian and his son revolted against the emperor Maximinus, but they were soon defeated by the Third legion Augusta. However, events in Rome led to the accession of Gordian's son grandson, and the young man immediately disbanded the unit responsible for the death of his father and grandfather. This was the moment on which the settlers proved what kind of men they were: instead of moving away now that the army had left them, they decided to stay and fortify their farms. If Rome abandoned them, they would do the job themselves. This land was their land.

The centenarium at Qasr Banat. Photo Marco Prins.
The centenarium at Qasr Banat.

The fortified farms were called centenaria (sing. centenarium). More than 2,000 have been identified, like the ones in Gheriat esh-Shergia, Qasr Banat, and Suq al-Awty. There appears to have been some central planning on regional level, because they all have a more or less identical square ground plan, and are only found in the Tripolitana. They were connected by a network of watchtowers.

When the Third legion Augusta was in 253 reconstituted by Valerian, the defense system had been changed beyond recognition. The armed peasants in the borderland, and not the garrisons of the three forts in the oases, were the first to notice an enemy, and would signal the inhabitants of other farms. In a short time, they could gather a considerable force that could probably repel a small nomadic army, or, in any case, slow it down sufficiently long for the legionaries to arrive. After all, the nomads would not have found it easy to storm a centenarium. Of course invaders could pass along the peasants and meet the legion head-on, but in that case, they would be caught between the Roman main force and the inhabitants of the centenaria - quite unpleasant when you do not have access to a well.

The Byzantine church at Suq al-Awty. Photo Marco Prins.
The Byzantine church at Suq al-Awty.

This shift towards self-defense was not unique. When in 260 the empire found itself caught in a deep military crisis, one Vaballathus organized the Euphrates frontier and a man named Postumus did the same along the Rhine. Here, we can see the growth of an identical division between a force of armed peasants, the limitanei, and a main force, often on horseback, working together in a system of two lines. By the time of Constantine the Great (306-337), this development had been completed.

After Antiquity

The frontier civilization of the Limes Tripolitanus survived the Roman Empire, although with some difficulty, because the cities went into decline. However, the rural areas managed to cope with the change. In the fifth century, the Tripolitanans had to fight against a new enemy: the Vandals, a European tribe that had fought itself a way through Gaul, Hispania, and Numidia and had settled in Carthage. For the first time since the Tripolitana had been conquered by the Romans, it became a real war zone. Riders on horse had to fight against warriors on dromedaries.

In 533, the Byzantine emperor Justinian sent his general Belisarius to restore order. New garrisons were stationed in the three cities, where the sixth-century walls are still visible. The centenaria remained and some of them even became real palace villas called castra, like the one at Suq al-Awty, where a visitor can not only see the remains of the boundaries of the ancient fields, but also the ruin of a Byzantine church. The olive oil production increased and appears to have been larger than ever and the countryside was wealthy, making the Tripolitana an almost natural target for Laguatan and Islamic expansion.

The regime change did not intervene with the economical or social structures. The linguistic change was small: many people still spoke Punic, and for them it was easy to learn Arabic. The centenaria/castra from now on being called qasr, pl. qsur. Except for a new religion, the predesert civilization that was based on careful water management and constant vigilance remained the same. It was only in the eleventh century, when two Arabian dynasties, the Zirids and the Fatimids, were involved in a major war, that the system collapsed. After the garrisons had been transferred from the cities to the front, nomads of Banu Hillal tribe could capture the qsur. The agricultural production declined rapidly, the cities were no longer fed, and the remaining town dwellers abandoned Lepcis Magna and Sabratha to settle in Oea, which was from now on known as Tripoli. The twelfth-century Sicilian geographer Muhammad al-Idrisi writes:

Foundation inscription of the fort of Si Aoun (Tunisia). Cast from the Museo nazionale della civiltà romana, Roma (Italy). Photo Jona Lendering.
Foundation inscription of the fort of Si Aoun (Tunisia). Cast from the Museo nazionale della civiltà romana, Rome.

Until recently, the Tripolitana was well-exploited and covered with fig trees, olives, dates palms, and other fruit trees. But the Arabs have completely destroyed this prosperity. The peasants were forced to leave the country, the orchards were destroyed, and the canals were blocked.
What had for eight centuries been a wealthy province of the Roman, Byzantine, and Muslim empires, now became a desert again. The decline of the population meant that there was no one who could destroy the ancient cities, the qsur, the watchtowers, the forts. They were simply left as they were, until nine centuries after the collapse, the first archaeologists started to study them.

The excellent state of preservation makes the forts of the Limes Tripolitanus unique. Another reason is that there are few places on this planet where you can see the immense power of a Roman emperor. To protect his home town, Septimius Severus changed an entire ecosystem, and the result lasted for more than eight centuries. For this display of power, world history offers no parallel.


  • Graeme Barker e.a., Farming the desert. The UNESCO Libyan Valleys Archaeological Survey (1996 Paris and Tripoli)
  • Anthony Birley, Septimius Severus. The African emperor (1988 New Haven, Conn.; 2nd edition).
  • Margot Klee, Grenzen des Imperiums. Leben am römischen Limes (2006 Stuttgart)
  • W.F.G. Lacroix, Africa in Antiquity. A linguistic and toponymic analysis of Ptolemy's map of Africa (1998 Saarbrücken)
  • Jona Lendering, 'Sherds from the Desert. The Bu Njem Ostraca' in: Ancient Warfare 1/2 (2007)
  • David Mattingly, Roman Tripolitana (1995 London)
  • Erwin Ruprechtsberger, Die römische Limeszone in Tripolitanien und der Kyrenaika, Tunesien - Libyen (1993 Aalen; Limes Museum)
  • I. Sjöström, Tripolitania in Transition. Late Roman to Islamic Settlement (1993 Aldershot)
© Jona Lendering for
Livius.Org, 2006
Revision: 13 Dec. 2008
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