Battle of Ad Decimum The Battle of Ad Decimum took place on September 13 , 533 between the armies of the Vandals , commanded by King Gelimer , and the Eastern Roman Empire ( Byzantine Empire ) , under the command of general Belisarius . This event and events in the following year are sometimes jointly referred to as the Battle of Carthage , one of several battles to bear that name . The Roman victory marked the beginning of the end for the Vandals and began the reconquest of the west under the Emperor Justinian I . Preparations . Ad Decimum ( Latin for " " Ten Mile Post " " , literally " " at the tenth " " ) , was simply a marker along the Mediterranean coast south of Carthage . Gelimer , with 11 , 000 men under his command , had advance warning of the approach of Belisarius ' 15 , 000 - man army and chose to take a strong position along the road to Carthage near the post marker . He divided his forces , sending 2 , 000 men under his nephew Gibamund across a salt pan in an effort to flank Belisarius ' army , which was advancing in narrow columns along the road . Another Vandal force , under Gelimer ' s brother Ammatas , was assigned to initiate a holding action at a defile near Ad Decimum . If everything worked well , Gelimer ' s 7 , 000 - man main body would follow Gibamund around the Roman left flank and cut off their retreat . Battle . Gibamund failed to accomplish his mission , as a force of Romans and Hun mercenaries drove his 2 , 000 - man force off and killed him . Ammatas also failed ; he arrived at the defile with his men still strung out along the road back to Carthage , and he too was killed . The Romans pursued his men all the way to the gates of Carthage itself . Gelimer ' s main force , however , inflicted serious casualties on Belisarius ' s troops along the main road . Belisarius ' s mercenary cavalry was routed by the Vandals , and even though Gelimer was outnumbered , his men were performing well in the fighting . It appeared as though the Vandals would win the battle . But when Gelimer reached Ammatas ' s position and discovered that his brother had been killed , by the vanguard of John the Armenian , he became disconsolate and failed to give an order for one more assault — which would probably have destroyed the reeling Roman army and cut off the Huns and Romans who had earlier advanced toward Carthage after beating Ammatas and Gibamund . Instead , the Vandal attack was weakened while Gelimer buried his brother on the battlefield . Given a respite , Belisarius was able to regroup his forces south of Ad Decimum and launch a counterattack , which drove the Vandals back and soon routed them . Gelimer was forced to abandon Carthage . Aftermath . Belisarius camped near the site of the battle , not wanting to be too close to the city at night . The next day he marched on the city , ordering his men not to kill or enslave the population ( as was normal practice at the time ) because he stated the people were actually Roman citizens under Vandal rule . They found the gates to the city open , and the army was generally welcomed . Belisarius went straight to the palace and sat on the throne of the Vandal King . He then set about rebuilding the fortifications of the city , and his fleet sought shelter in the Lake of Tunis , five miles ( 8 km ) south of Carthage . After a second defeat at the Battle of Tricamarum later in the year , the Vandal kingdom was all but ended .