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Ad Decimum September 13, 533
Strategic Context
Emperor Justinian of the Eastern Byzantine Empire is trying to reconquer the Western Byzantine Empire and restore the old glory of the Roman Empire. Many lands remain to be conquered when the usurped Vandal King Hilderic appeals for aid against his cousin, Gelimer, who is much less friendly to Byzantine interests. Justinian sends his best general, Belisarius, to Africa with an expeditionary force to defeat the Vandals and reestablish control over Carthage, North Africa, and the Mediterranean. Belisarius lands his army in North Africa near Triplolitana and begins the day march on Carthage. Knowing Carthage’s fortifications to be in decay, Gelimer plans to ambush the Byzantine army.
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Stakes
+ A Byzantine victory would return North Africa to the Byzantine Empire.
+ A Vandal victory would prevent Byzantine expansion to North Africa and continue to challenge for control of the Mediterranean.
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By Jonathan Webb, 2009

2. Ad Decimum, 533 Strength Byzantines Well Vandals Well Belisarius
Gelimer
15,000
11,000
By Jonathan Webb, 2009

3. Eurasia c. 500
BYZANTINE EMPIRE

4. The battlefield consists of a section of Roman road running between Tripolitana to the east, and Tunis and Carthage to the west, all well off-map. This section of the road features a narrow defile running through rough, hilly terrain. The battlefield is enclosed to the north off-map by the Lake of Tunis. The Byzantine objective is the western end of the defile to continue the march on Carthage.
Byzantines
(Belisarius)
Vandals
(Gelimer)

5. Vandals (Gelimer) 11,000 Byzantines (Belisarius) 15,000
Without a coherent leader the Vandals become disorganized themselves but are still capable of being a potent fighting force. Belisarius therefore launches a sudden full scale attack before Gelimer regains his composure and assumes control again. This attack eventually breaks the Vandal army and the Byzantines pursue the Vandals from the battlefield.
A stroke of fortune helps Belisarius recover from the initial surprise: Gelimer arrives at the front to find his brother Gibamund slain. Gelimer is overcome with sorrow and insists his brother be buried immediately right there on the battlefield. During this time, heavy fighting continues but Gelimer does not push the attack, granting Belisarius the necessary time to coordinate his infantry into a cohesive mass.
The fierce, congested melee is won by the heavier Byzantine cataphract cavalry, which kill Ammatus and chase the Vandal cavalry away before turning back to aid their fellow mercenary cavalry. They arrive too late however as Gelimer’s main cavalry force joins the battle and routs the Byzantine mercenary cavalry. Just as the Byzantine infantry appear on the verge of straightening out their ranks, the main Vandal cavalry force crash into them, further disordering them. Belisarius marshals his force as best he can to maintain his force’s survival.
Belisarius’ force proceeds westward with cavalry deployed to guard the front and rear of the infantry columns. Gelimer divides his force into three groups to ambush the unsuspecting Byzantines. Gelimer deploys a cavalry force under Ammatas to establish a blocking position near a steep defile. Gelimer deploys another cavalry force under his brother Gibamund further south to hit the Byzantine left flank. Gelimer commands the main cavalry force, which lays in wait to envelop the Byzantine rear.
Ammatas’ cavalry engage the Byzantine advance guard while Gibamund’s cavalry hook around its left flank. Belisarius quickly checks this second force with his own cavalry and a fierce melee ensues at the front of the column. Meanwhile, Belisarius struggles to organize his infantry to join the battle.
Vandals
(Gelimer)
11,000
Byzantines
(Belisarius)
15,000
Byzantines
(Belisarius)
Ammatas
Vandals Byzantines
Cavalry Cavalry
Infantry
Gibamund
Gelimer
Symbol guide
Vandals
(Gelimer)

6. Ad Decimum, 533 Casualties & Aftermath
Byzantines:
Vandals:
≈2,200 or
20%
≈750 or 5%
Belisarius encamped for the night before marching into Carthage the next day. Belisarius declared the city’s citizens to be Romans oppressed by Vandal rule and issued orders for their fair treatment. The Byzantines found the city gates open and Belisarius set about improving the city’s fortifications against the resilient Vandal kingdom. Belisarius defeated Gelimer and the Vandals for good later the same year at the Battle of Tricamarum.
By Jonathan Webb, 2009

7. The Art of Battle: Animated Battle Maps
By Jonathan Webb, 2009