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Battle of Ad Decimum

(13 September 533 CE)

This post is also available in: Polish (polski)

Belisarius on the mosaic
Belisarius on the mosaic

Battle of Ad Decimum was the first battle fought in the Roman campaign in Africa in 533-534. It was of great importance for the efforts to regain the African provinces. The Vandal Army was significantly depleted with negligible losses.

Landing in Africa

The fleet carrying the Roman army under the command of Belisarius, a talented commander immensely loyal to Emperor Justinian I, arrived after a troublesome trip to the African coast in the Caput Veda region on August 31, 533. After landing, earthen fortifications were erected under which the army could spend the night and rest untouched by surprise attack.


As soon as the news of the Romans landing reached Gelimera, he set off to stop the enemy in the valley at Ad Decimum. The Vandal Army was divided into two groups, Gelimer with part of the army was in Hermione, and his brother Ammatus, who led the second group, was stationed in Carthage. The two groups were to meet and join at Ad Decimum, about 13 km from Carthage.

According to Ian Hughes, the Vandals could put up to battle no more than 13,000. soldiers, but other authors give much higher numbers.

Coin with the image of Gelimera.

Gelimer, experienced with actions against the Moors, decided to set an ambush for the Romans in the Ad Decimum valley. The task of Ammatus (up to 7,000 warriors) was to strike from the north and push the Romans deeper into the valley, causing confusion in their ranks. Gelimer (up to 6,000 warriors) was to fall on the squattered troops from the south. The chief sent 2 thousand people to Gimabundus by a road bypassing Ad Decimum to garrison the abandoned Carthage.


Ian Hughes estimates that Belisarius had an army of probably less than 16,000. (so many were to go on the expedition, but many died on board ships) soldiers (not counting the crews of ships). He set off towards Carthage, but he was cautious – mindful of the experiences of the unsuccessful expedition against the Vandals of the 5th century and tried to protect himself against a sudden attack by all means. The troops marched as follows:

  • in the vanguard, John of Cappadocia, at the head of 300 bucellari (selected mercenaries employed by the commander), whose task was to conduct reconnaissance approx. 3.5 km ahead of the main forces,
  • Sinnion and Balas, led by 600 Huns, marched to the left of the main column, also about 3.5 km from it, also conducting reconnaissance operations,
  • main forces,
  • the right flank was covered by a fleet, moving on a par with the land forces,
  • in the ariergard marched Belisarius at the head of his bucellari and comitatus (elite bodyguards), from where he was able to quickly proceed to the part of the main force threatened by the enemy.

The march took place without any obstacles, and the Romans were enthusiastically welcomed by the local population, which, although it had been under the rule of the Vandals for about 100 years, maintained its separateness and retained its Roman character. The army covered about 14.5 km a day.

The first skirmish between the Roman forces and the Vandals took place at Grasse, where Ariergard Belisarius clashed with a unit sent by Gelimer. This foreshadowed the most difficult section of the road – when the army had to split from the fleet as the road turned inland.


Belisarius thwarted Gelimer’s plans before the battle, deciding that he was not yet ready for battle, as he did not have enough news of the enemy. With this in mind, he chose the best place to set up a camp, ie approx. 6.5 km before the valley. He ordered the infantry to build a camp, leaving the camps there with his wife Antonia. To aid John of Cappadocia, he sent Solomon in command of the foederati (allied barbarians), and he himself moved towards Ad Decimum. The intention of the Roman general was to recognize the Vandal forces, then return to the camp for the night and fight a battle the next day. Meanwhile, Ammatus was rapidly approaching the valley at the head of a reconnaissance preceding the rest of his troops.

Phase I

The Gibamundus squad sent to Carthage stumbled upon a single Huna who had gone out to meet them. The warriors stopped. Then the Huns struck furiously. The Vandal unit was annihilated and its commander killed. In this clash, the ratio of Huns to Vandals was 1: 3.

Phase II

The reasons why Ammatus did not group his army before entering the Ad Decimum area are unclear. Vandal troops marched in a long column, in groups of about 30 warriors, while the king himself, at the head of scouts, rode ahead of the main forces, wanting to recognize the enemy’s forces before the clash.

When around noon the chief of the scouts entered the valley, he encountered the detachment of John of Cappadocia. In a fierce clash (apparently Ammatus himself killed 12 bucellari), the Vandals were defeated, Ammatus was killed, and the remnants of scouts fled towards Carthage. John and his troops gave chase, cutting out groups of warriors on their way to the city, unable to put up an organized resistance to the Romans.

Soon the remnants of Ammatus’ group fled, and Jan stood at the gates of the city.

Phase III

Solomon, marching at the head of foederati and trying to join John, reached the scene of his encounter with Ammatus. Climbing a nearby hill, his soldiers noticed an approaching cloud of dust – a harbinger of the approaching Gelimer’s Vandals. Solomon sent a messenger to Belisarius for backup.

There was a hill between Solomon’s troops and Gelimer’s troops, perfect for setting up a camp. Realizing its importance, both sides rushed to take the apex. The Vandals were the first to reach it, a fight ensued in which foederati were repulsed, and then rushed to flee. Having reached the position of Belisarius’ personal guard (800 men) led by Uliaris, they kidnapped these soldiers with their fear and rushed towards the position occupied by the leader himself.

Only Belisarius managed to re-form the cavalry. After hearing the reports of the arriving officers, the Roman commander decided to immediately attack the heavily weakened Vandals.

Meanwhile, an event that determined the further fate of the battle took place – Gelimer found the body of his fallen brother and instead of pursuing foederati, or crushing the unit of John of Cappadocia, busy looting the bodies of killed Vandals on the way to Carthage, he began to consider your position. He mistakenly assumed that most of the Roman forces had probably already left the valley and, having beaten Ammatus’s troops, set off for Carthage. This moment of indecision gave the Romans the necessary time.

Phase IV

When Gelimer decided to move towards Carthage and attack the Roman army from the rear, which he believed was in the open countryside outside the city, he was suddenly attacked by the reorganized cavalry of Belisarius.

The Romans quickly broke the ranks of the barbarians unprepared for battle and dispersed their forces. Gelimer almost miraculously survived and with the rest of the warriors, he ran to flee, but not towards the city, because he was still unaware of the true picture of the situation. Avoiding Carthage, he headed west. Thanks to this, the very next day Belisarius was able to triumphantly enter Carthage.

Map showing the expansion of the Eastern Roman Empire in the 6th century under the rule of Justinian the Great. In red (year 527), the lands that took over the state at the beginning of Justinian’s reign are marked. The orange colour represents the war achievements of Belisarius for the year of his death 565.
Atlas historique de Georges Duby | Under Creative Commons Attribution-Share Alike 2.5 Generic license


The Battle of Ad Decimum was of great importance for the efforts to regain the African provinces. The Vandal Army was significantly depleted with negligible losses. Carthage was conquered – the administrative centre of the kingdom of Gelimera, and an area of ​​great economic importance was captured. From then on, the Vandals had to strive for the fastest possible fight again, because in this situation they had no chance of winning the war to exhaustion. Moreover, the defeat of the hitherto invincible Vandals sowed doubt in their new allies – the Moors, which meant that most of them remained neutral in the upcoming events.

Author: Krzysztof Kaucz (translated from Polish: Jakub Jasiński)
  • Robert Browning, Justynian i Teodora, 1971
  • Ian Hughes, Belizariusz Wódz Bizancjum, Poznań 2016

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