Tactical Use of Static and Mobile Linear Barriers

The distinctions in the case of static barriers can become blurred. For example, in certain locations some linear barriers appear originally to have been temporary in intention, but may have then become long term fixtures. Looking at the Corinthian Isthmus, the stone wall built by Anastasius and rebuilt by Justinian was intended to be permanent and some of it is still there. Other walls which were built to stop Xerxes or Epameinondas were clearly temporary. The site of Artaxerxes’ Trench may have been reused for the Wall at Macepracta, described by Ammianus Marcellinus, and is possibly now the location of the Wall at Umm Raus. Also, while the objective may be different, the working principle was similar – namely, the use of a continuous physical object (a wall) or a void (a ditch) to obstruct the progress of the threat in the direction of the builder.

The use of mobile linear barriers in the context of sedentary states fighting battles against nomads is common. Static linear barriers provided the means to block the progress of mounted nomads and as a defence against their stinging arrows. Therefore, it might be a logical progression, rather than to wait until the threat comes to the fixed barrier, to make the barrier mobile and take it to the threat.

The exercise of looking at the use of temporary and mobile barriers might be valuable in showing how linear barriers fitted into a broad spectrum of such barriers in general.

1: Role of linear barriers on the battlefield and in passes

One-time threats

Many very substantial linear barriers have been constructed across areas where an expected one-time threat would cross. Linear barriers which have already been mentioned include the following: Cnidus’ Reşidiye peninsula canal, which was started but remained unfinished during the reign of Cyrus; the Corinth Isthmian walls, built to block Xerxes’ Persians; Ataxerxes’ Trench, cut before the Battle of Cunaxa (401 BC); and the Wall of the Judean King Alexander Jannaeus (103–76 BC), who tried to stop the Seleucid King Antiochus Dionysus.

Other examples include: Crassus’ Servile War Wall, built across the toe of Italy on the Rhegium Peninsula, in order to contain Spartacus and his rebel slave army; Caesar’s earthwork to block the Helvetii who were trying to migrate to Gaul in 58 BC; the Teutoburg Forest Wall, built parallel to the routeway, from behind which the Germans could attack the Romans; and at Hakata Bay where in 1281 the Japanese faced a second attack from the Mongol and Korean forces commanded by Kubilai Khan. (The Japanese had built a stone faced embankment more than twenty-two kilometres along the coast about three metres high and wide, after the first attack in 1274 was broken up by storms and Japanese resistance.)


A clear category emerges where passes were fortified or refortified with linear barriers in order to strengthen the positions of the defenders. A pass is an obvious place for a defending power to force a battle, as the narrowness of the location helps make the task of the defender easier against a larger attacking force.

Thermopylae, where the Greeks delayed the Persian advance in the fifth century BC, has already been discussed. In the following century the situation was reversed. In 330 BC Alexander the Great advanced on Persepolis, leading 20,000 troops across the Zagros Mountains and onto the ten kilometre-long pass of the Persian Gates. The local satrap Ariobarzanes built a wall across the pass and forced Alexander to retreat. Reversing the story of Thermopylae, the Greeks followed a local guide up treacherous paths onto the plateau above the pass, and then crept up behind the Persians who were annihilated in a joint attack from behind and in front. This manoeuvre left open the road to Persepolis for Alexander.

In 192 BC the Seleucid King Antiochus III invaded Greece and was confronted by the Romans, here the invader, rather than the defender, built the wall. ‘There Antiochus built a double wall on which he placed engines. He sent Aetolian troops to occupy the summits of the mountains to prevent anybody from coming around secretly by way of the hill called Atropos, as Xerxes had come upon the Spartans under Leonidas, the mountain paths at that time being unguarded.’ The Romans, under Marcus Porcius Cato, like many others, got round behind Antiochus using the mountain path – forcing him to withdraw. Later in 146 BC the Romans forced their way through Thermopylae in order to put down a Greek revolt.

The Bulgars and the Byzantines had a joint history of battles in barricaded passes. In 811 the Byzantine Emperor Nicephoras I laid waste to Bulgaria and burnt the capital Pliska. On hearing that the Bulgarians were defending the passes, Nicephoras set out for the Vǎrbitsa Pass on the route back to Constantinople where the Bulgars had built a wooden wall. The Byzantines tried to burn the barricade and were either themselves burned or drowned in the moat built behind the wall. Victory went the other way in 1014 when Bulgar Khan Samuil built a wooden wall across the pass at the village of Klyuch, or Kleidion meaning key, in the Haemus Mountains which provided the main invasion route into Bulgaria. In the summer of 1014 the army of Basil II was repelled at the wall. Again, a path behind the wall was found and the Bulgarians were overwhelmed.

A Letzimauer, or Swiss stone wall, played a key part in the Battle of Stoss Pass in 1405 in the Appenzell Wars between 1401 and 1429, when the local populace from the region fought off the Hapsburgs. Appenzell’s force of 400 men defended the wall at the Pass against which 1,200 Hapsburg soldiers were suffocated or halberdiered.


Although many battles have been fought at passes most took place on more open ground. Even here there was a consistent record of the use of linear barriers.

When heavily outnumbered, Caesar built a linear barrier in 48 BC, around the forces of Pompey who were camped on the coast of north-western Greece below Dyrrhachium. The barrier was twenty-two kilometres long and included four forts. Pompey’s forces also constructed a linear barrier. If anything, this was testimony to the wall-building capacity of the legionary which could be put to use making more permanent linear barriers.

In 484 the Sasanian Shah Peroz led an army against the Hephthalite chief Akhunwar who was crossing the Gorgan Plain to the east of the Caspian Sea. Procopius describes how the Persians (Sasanians) ‘gave chase at full speed across a very level plain, possessed as they were by a spirit of fury against the enemy, and fell into the trench, every man of them.’ Peroz was killed and his army routed. The Sadd-i-Iskandar may have been built subsequently by the Sasanians in order to counter the Hephthalite threat.

The nomadic Arabs proved adept users of tactical linear barriers. In AD 627 Mohammed led roughly 3,000 defenders of Medina against a confederate Arab and Jewish army more than three times its number. The Muslims dug a trench – hence the name the Battle of the Trench – which negated the enemy’s superiority in numbers and cavalry; soon the siege was lifted and the confederacy collapsed. Having proved impossible to dislodge from Medina, Mohammed was able to return in triumph to Mecca.

After the ninth century, linear barriers intended for long term use appear increasingly to have fallen out of use in Europe. This might have been because of the improvements in the military technology of point defences, like burghs and castles, and the mobility of mounted men at arms. The technology employed by infantry improved in turn, to the extent that they could fight off heavily armoured mounted knights by using a combination of weapons of extended reach, like pikes. They also used projectile weapons, for example longbows, and battlefield linear barriers which might be either static or mobile. Thus, linear barriers returned to the military repertory in a somewhat different and now predominantly tactical, battlefield form.

By the fourteenth century, infantry had increasingly got the measure of cavalry. Obstacles were built on the battlefield in the form of ditches – often filled with spikes and other horrors to increase the lethality of plunging into them. These served to channel and break up the momentum of mounted men at arms. In 1385, for example, the Castilians invaded Portugal, met an army reinforced by a contingent of English archers, and were soundly beaten. Excavations of the Aljubarotta have revealed a ditch about 240 metres wide across the Portuguese front and numerous pits. In 1387 the English commander of the mercenary White Company in Italy, Sir John Hawkwood, drew up archers behind drainage dykes at Castagnaro. At Agincourt in 1415 the English archers built a barrier of sharpened stakes which they carried with them. These allowed the construction of a mobile palisade. Indeed, when the French declined to attack, the English literally upped their sticks and reformed closer to the French lines, the better to provoke them into attack with a barrage of arrows.

Linear barriers used on the battlefield demonstrate that ancient and Middle Ages rulers and commanders did not suffer from any prejudice against their deployment. The point is that earlier leaders were flexible in their willingness to consider the value of linear barriers in a whole range of situations, both immediate and long term, and tactical and strategic.

2: Defeating nomads on open ground – mobile linear barriers

The armies of sedentary states found it almost impossible to defeat a nomad horde that was well-led on open ground. The combination of mobility and bow-and-arrow power meant that such armies could destabilise and decimate the more static armies of sedentary states. Even if the body armour of elite troops could stop the nomads’ arrows, a terrible toll would still be taken of less well armed soldiery and horses. Nomad armies were, however, occasionally beaten. Crusaders defeated a Turkish force of mounted archers at the Battle of Dorylaeum (1097) where a line of heavily armed dismounted knights defended less well armed compatriots, until reinforcements attacked the Turks in the rear. At Ain Jalut (1260) the Mamluks induced the hitherto invincible Mongols into an ambush by feigning retreat. The Mamluk forces used midfa, or portable hand cannons loaded with explosive gunpowder, to incite fear and disorder among the Mongol cavalry.

These battles anticipated the means to defeat nomad forces – the protected line that blocked arrows, and the explosive energy from gunpowder. If the line could be composed of a solid yet moveable inanimate material, one that obstructed nomad arrows, and incorporated crossbows and firearms that could outrange nomad projectiles on a flat trajectory, then the terms of battle could be more than equalised.

Linear barriers did not need to be static. They could be put on wheels or sledges and taken to the enemy. That way protection could be provided against nomad arrow storms and cavalry attacks. Meanwhile, the mobile barrier could provide a fortified screen through which the defenders’ bows, crossbows, firearms and cannon raked the enemy.

At the Battle of Mobei in 119 BC the Han general, Wei Qing, used rings of heavily armed chariots, or wu gang, first to break Xiongnu charges, and then to launch a successful counter-attack. These vehicles protected infantry and crossbowmen from Xiongnu arrows and gave them the security to be able to shoot back accurately. Han cavalry dealt with any Xiongnu who broke through.

Mobile linear barriers could be improvised of the most obvious available vehicle used by most armies, that is, the wagon or cart, which had always been used to protect camps during halts and to defend camps behind the main battlefield. Mobile defences in Europe were developed first against non-nomad forces. For example, in 1428 at Rouvray, Sir John Fastoff, anticipating attack by larger forces, formed their convoy of carts into an enclosure. By the fifteenth century war wagons were being specially designed so that mobile barriers could be formed. The most famous war wagons were perhaps those of the Hussites, led by Jan Žižka in the early fifteenth century, and known as vozová hradba or wagon walls.

Gulyay-gorod reconstruction.

The Russian Gului-gorod, used in the sixteenth and early seventh centuries, have already been discussed. The Battle of Molodi in 1572 – where the protection afforded by the Gului-gorod was critical – perhaps marked a turning point in the fight between settled states and nomads. It has been seen how static linear barriers built by the Russians played a crucial part in closing down the Pontic Steppe. At the same time the Russians also used mobile linear barriers to defeat the nomads in the field.

These developments in military technology ultimately meant that the fight could be taken to the open ground preferred by nomad hordes of mounted archers, and for them to be defeated there. The importance of Molodi is not perhaps sufficiently recognised in the West – for never again did a major nomad army invade a great empire.


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