Battle of Ad Decimum: Byzantines Defeat Vandals During Reconquest of North Africa

« Previous story
Next story »
Battle of Ad Decimum: Byzantines Defeat Vandals During Reconquest of North Africa

Major nations of Mediterranean area, c. AD 526
Image from "Historical Atlas" by William R. Shepherd from University of Texas Libraries
(Unless otherwise indicated, all illustrations are courtesy of Wikipedia)

Today in Military History: September 13, AD 533

My mini-history lesson of the day is devoted to a battle between the East Romans (Byzantines) and the Vandals, one of the several Germanic tribes which contributed to the collapse of the West Roman Empire in the mid-fifth century AD.


After the last Roman emperor was deposed in 476, western Europe splintered into a plethora of minor barbarian kingdoms. Fortunately, the East Roman Empire (more commonly known today as the Byzantine Empire) continued the legacy of the Caesars in the eastern Mediterranean region. With their capital in Constantinople, the Byzantines continued to nurture Roman civilization. Before long, the Byzantine emperors began toying with the idea of reacquiring the lost lands of the western Mediterranean. These dreams were given legs in the 530's, thanks to a "regime change" in a rival north African kingdom.

One of the barbarian kingdoms that contributed to the disintegration of the western Roman world was the Vandals. This Germanic group was one of several tribal groups – including the Visigoths, Ostrogoths, Franks, Suevi, Heruls and others – that migrated into Gaul (modern France) from central and eastern Europe in the early fifth century AD. The Vandals' sack of Rome in 455 became legendary; it also supplied the word "vandalism" to our language for the ruthless destruction of anything beautiful or venerable.

Eventually, the Vandals moved through southern France, Spain and finally into northern Africa. As a result of their movement and war-like spirit, they created a kingdom that encompassed what is today Tunisia, the coasts of northern Algeria and western Libya, the Balearic Islands, Malta, Corsica and Sardinia, with their capital in the rebuilt city of Carthage. This area was one of the main breadbaskets of the old Roman Empire. The Vandal occupation of this fine agricultural land put the Roman Empire in a precarious situation.

Figure from sixth century mosaic in Church of San Vitale, Ravenna, Italy; Believed to be Belisarius; Image courtesy of
Figure from sixth century mosaic in Church of San Vitale, Ravenna, Italy
Believed to be Belisarius; Image courtesy of

Although the Vandals had converted to Christianity during their time in the West, their brand (known as Arianism) was not quite the same as the Byzantines. When Gelimer became ruler of the Vandal kingdom in 530 (by deposing his brother), he began to oppress Catholic Christians. Because of these persecutions, Byzantine Emperor Justinian I finally declared war on the Vandals. [It didn't hurt the East Roman cause that a long war with Sassanid Persia ended in 532, with a Byzantine-favorable treaty.] In mid-533, Justinian sent an army under the command of his most trusted general, Belisarius, to take down the Vandal kingdom.

Byzantine Army

This army had 10,000 comitatenses and foederati infantry. The comitatenses were field army troops – not troops assigned to garrison duty in cities or border forts – who were experienced campaigners. The foederati were groups of soldiers recruited from allied states – usually barbarian peoples living within the boundaries of the Byzantine Empire – who were required by treaty to provide troops when needed. In addition, about 3000 cavalry, some Byzantine and some foederati, were recruited for the Vandal expedition.

Rounding out the Byzantine cavalry forces were 600 Huns and 400 Heruls – all mounted archers – and 1500 mounted bucellarii of Belisarius' personal retinue. [The name means "biscuit-eaters."] Belisarius had recruited these warriors when he was a young man, and he trained them to fight not only with the lance and sword, but also the intricacies of using a composite bow similar that used by the Huns and other Asian steppe warriors. In addition to the bow, the "biscuit-eaters" also made use of a weapon known as a plumbata, essentially an early version of a modern lawn dart (see illustration below). With an iron head and a lead weight, it was incredibly effective against enemy infantry at close range.

Sixth century Byzantine bucellari, artist unknown; Image courtesy of
Sixth century Byzantine bucellari, artist unknown
Image courtesy of

Vandal Army

The Vandal army which opposed Belisarius is a little more conjectural. It totaled about 11,000 warriors all told – although some historians speculate it was closer to 30,000. This army was likely an all cavalry force, as the Vandal army for hundreds of years was mostly heavy horsemen, with a smattering of lighter horsemen. It is possible that some of the light horsemen were members of subject Moorish tribes.

Prelude to the Battle

On June 24, 533, the Byzantine force of 16,000 men sailed on 500 transports protected by 92 dromons, or warships. After sailing along the coast of Greece and southern Italy, the East Roman fleet put into the Sicilian port of Syracuse, which was ruled by the Ostrogoths, who were at that time on friendly terms with the East Romans. Procopius, Belisarius's personal secretary – and later historian of the Vandal War – found out about a revolt against Vandal rule had broken out in Sardinia. In response, Gelimer sent his brother Tzazon with 5000 soldiers and most of the Vandal fleet to quell the uprising. In addition, the province of Tripolitania – the eastern coastal area of the Vandal kingdom – declared its independence from their barbarian overlords. This act provoked no response from the Vandals.

When told of these event, Belisarius almost immediately ordered his army to re-embark, and the Byzantine fleet sailed and easily landed in North Africa against no naval opposition in early September. Belisarius landed his army and began marching toward Carthage. Shortly after landing, Byzantine and Vandal scouts skirmished, finally alerting King Gelimer to the presence of enemy forces almost on his doorstep. [Modern historians marvel that the Vandals were completely in the dark about the East Roman attack, despite preparations taking over a year since the end of the war with the Sassanid Persians.]

Once he learned of the East Roman assault on his kingdom, Gelimer moved quickly, sending a message to Tzazon to return to Carthage with his troops. He assembled his army quickly, dividing it into three parts. One Vandal force of about 2000 men under command of his brother Ammatus was to march south of Carthage, and deploy near road post marker Mile 10 (which gave the coming battle its name, from the Latin "Ad Decimum"), which probably also boasted a way station or caravanserai for travelers. Next, a second group of 2000 Vandals under his nephew Gibamund, approaching from the southeast, would set an ambush near Ad Decimum in a saltpan (a flat expanse of ground covered with salt and other minerals, usually found in deserts; see map below). Then, to close the trap, Gelimer and the remainder of his warriors – who were shadowing the East Romans to the south of their line of march – would attack the Byzantine army from the rear, effectively cutting them off from their camp or their fleet.

Vandal battle plan for battle of Ad Decimum
Vandal battle plan for battle of Ad Decimum

It was a bold and ambitious battle plan, worthy of a Byzantine general. There were two problems with it: the coordination needed for its success was not an earmark of the Vandal military ranks; and, King Gelimer himself had no previous military experience. His lack of skill in this arena would be exposed, and it would not go well with him or his army.

Battle of Ad Decimum: First Phase

Battle of Ad Decimum; first phase; Image created by Cplakidas, Wikipedia user
Battle of Ad Decimum; first phase
Image created by Cplakidas, Wikipedia user

From the day of his East Roman army landing in Africa, Belisarius had taken precautions to avoid a Vandal ambush. On the morning of September 13, those plans bore fruit. A squadron of 300 Byzantine heavy horse commanded by John the Armenian scouted ahead of the army; the 600 Huns scouted to the left of the main road to Carthage, hoping to counter any ambushes. The remaining cavalry, with Belisarius and his bucellarii bringing up the rear, began a slow march on the coast road to Carthage.

Gelimer's battle plan began to unravel almost from the start. His brother Ammatus accompanied by his personal retinue arrived early near Ad Decimum, and rode forward to survey the terrain at about noon. Right on cue, John the Armenian and his Byzantine heavy horsemen arrived at the same moment. After a short, sharp battle, the East Roman cavalry killed Ammatus, which broke the fighting spirit of his warriors. They routed from the field riding hell-bent for leather back to the safety of Carthage. As they raced to the Vandal capital, they were closely pursued by the Byzantine cavalry, who cut the fleeing Vandals down with no mercy. The Byzantines arrived at the gates of Carthage shortly after the skirmish.

At about the same moment, the Hunnish reconnaissance force ambushed the Vandal force commanded by Gibamund his nephew, which was hiding in the saltpan south of Ad Decimum. In spite of the fact that the Asiatic horsemen were outnumbered more than three to one, they possessed one main advantage over the Vandals: The Huns skill with their composite bows. This single weapon gave them "command of the skies," bombarding the enemy cavalry with clouds of arrows before charging in and coming to grips with the Germanic warriors. According to historian J.B. Bury, "The Huns enjoyed the battle; the Vandals, they thought, were a feast which God had prepared for them."

Battle of Ad Decimum: Second Phase

Battle of Ad Decimum: Second Phase; Image created by Cplakidas, Wikipedia user
Battle of Ad Decimum: Second Phase
Image created by Cplakidas, Wikipedia user

At about this time, a squadron of foederati – the 400 Heruls – from the main Byzantine army arrived on the scene, seeing the site of the skirmish with Ammatus's force, and likely hearing the last phase of the Hunnic triumph over Gibamund's detachment. [By this point, the Huns were likely looting the bodies of the dead Vandals, and began pursuing the fleeing Vandals.] A range of hills separated the coastal road and the Ad Decimum waystation from the saltpan where the Huns had annihilated the Vandal flanking force. Seeking more information, the Heruls climbed a nearby hill. Once they reached the summit, they saw a large cloud of dust to the southeast. This was Gelimer and the balance of his army, thinking his plan was still intact, riding to envelope and destroy the Byzantines.

In minutes, Vandal scouts clashed with the Heruls, while the main force – numbering about 7000 warriors – came forward quickly and attacked the isolated foederati. Vastly outnumbered, the Herul horsemen fled in panic back toward the main Byzantine cavalry formations. They skirted the forward squadrons of the cavalry force and headed straight for Belisarius and his bucellarii. Uncharacteristically, the general's usually dependable retinue were themselves terror-stricken, and spontaneously fell back. Fortunately, Belisarius managed to rally his horsemen – giving them a stinging rebuke for their cowardly behavior – and ordered a rapid advance to Ad Decimum. He sent a message back to his fortified camp, ordering the infantry to march to the battlefield in support of his cavalry squadrons.

Battle of Ad Decimum: Final Phase

Battle of Ad Decimum: Final Phase; Image created by Cplakidas, Wikipedia user
Battle of Ad Decimum: Final Phase
Image created by Cplakidas, Wikipedia user

Shortly after driving off the Byzantines' Herul horsemen, King Gelimer and his followers descended the hill overlooking the battlefield where the initial fighting occurred. While examining the bodies of the Vandal slain, Gelimer discovered the body of his brother Ammatus; his brother's corpse was surrounded by a dozen East Roman horsemen he had personally slain. Upon seeing his sibling's lifeless body, Gelimer was overcome with grief. All consideration for defeating the Byzantines left his mind; Gelimer now became obsessed with giving his brother a proper burial on the battlefield where he lost his life.

The Vandal army promptly fell into disorder, without their king concentrating on preparing for an imminent attack by the Byzantine invaders. With Vandal squadrons wandering the battlefield, receiving no supplemental orders to reform, they were ripe for a sudden attack. Presently, Belisarius and his cavalry came thundering onto the plain south of Ad Decimum. Striking like a terrible swift sword, the Byzantine horsemen scattered the disorganized Germanic horsemen. Within minutes, the Vandal army was shattered and in retreat. Finally coming to his senses, Gelimer gave the order for his men to retreat west and south into the deserts of nearby Numidia. Roman pursuit of the Vandals lasted past nightfall. The battle of Ad Decimum was over.


As with most battles of the Dark Ages, casualty figures are tentative and mostly non-existent. The Vandal army no doubt suffered heavy casualties, while the Byzantine cavalry bore the brunt of dead and wounded in Belisarius's army.

Footnote #1: In the late afternoon of September 13, the Byzantine infantry made its way to the battlefield. Belisarius ordered a fortified camp built near the waystation. He was leery of marching into and occupying Carthage after dark. The next day, when the Huns and the troops of John the Armenian rejoined the main army, the Byzantine army marched the 10 miles to Carthage, fearing they would have to assault the city to occupy it. When scouts reported the city gates were open, Belisarius marched into the re-occupied city. He rode to the royal palace, sat upon the Vandal ruler's throne, and ate the victory feast Gelimer had ordered prepared for his coming victory.

Footnote #2: Belisarius warned his men to treat the people of Carthage like Roman citizens, rather than as conquered people. He also ordered the city walls of Carthage to be repaired; during the course of the Vandal occupation, any city with walls was ordered to have them pulled down, as a precaution against any town becoming the center for an anti-Vandal revolt.

Footnote #3: It took another year of combat before Gelimer finally surrendered to Belisarius. Despite the great expense on the Byzantine re-conquest of North Africa, the area remained under East Roman rule for only about 113 years. In AD 647 troops of the new Muslim Arab wave of conquest. The North African lands were now forever lost to the New Rome.

Footnote #4: For his success in North Africa, Belisarius was "rewarded" by Emperor Justinian with the assignment of recapturing Italy, then being ruled by the Ostrogoths. Again working on a shoestring budget and with limited numbers of troops, Belisarius conquered most of Italy south of the Po River between 535 and 540.

Posted in top stories | 0 comments
« Previous story
Next story »


* To comment without a Facebook account, please scroll to the bottom.

Add new comment

Plain text

  • No HTML tags allowed.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Lines and paragraphs break automatically.
This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.
Have a tip for us? A link that should appear here? Contact us.
News from the World of Military and Veterans Issues. Iraq and A-Stan in parenthesis reflects that the author is currently deployed to that theater.