Genseric (more correctly Gaiseric), king of the Vandals, was an illegitimate son of Godigiselus, who led the Vandals in their invasion of Gaul, and perished with 20,000 of his followers in a defeat by the Franks (407 A.D.), who were only prevented from completely destroying the Vandals by the timely intervention of the Alans. In the year 409 the Vandals, with their friendly allies the Suevi and the Alans, poured over the Pyrenees into Spain, and shared its territory between them. The Vandals were divided into two branches, the Asdingi, who settled in Galicia, and the Silingi, who occupied Bætica in the south. The latter, after suffering crushing defeats from the Romans, joined the former under their king Gunderic, son of Godigiselus, whose nation soon became the most powerful in the Peninsula. Gunderic died in 427, and was succeeded by Genseric. Invited to the invasion of Africa by Bonifacius, Count of Africa, who had been goaded on to rebellion through the machinations of his rival Aetius, the conqueror of Attila, Genseric first crushed the Suevi, and, after numbering his united Vandals and Alans on the Andalusian shore, crossed over to Numidia in 428. Only when it was too late did Bonifacius repent his treacherous designs and attempt in vain to drive back the Vandals. After a thirteen months' siege, in the course of which the great St Augustine died, the city of Hippo Regius fell (430), and was given over to all the fury of wanton and brutal outrage. With such ferocity did the Vandals lay waste and destroy churches, fields, and cities as to leave their name after fourteen centuries a synonym for destructive barbarism. All Africa west of Carthage quickly fell into the hands of Genseric, who seized that city itself in 439, and made it the capital of his new dominions. He dated his reign, which lasted thirty-seven years, from this conquest.
With a capacity for adapting himself to new conditions which shows his genius, he quickly built up a formidable maritime power, and his fleets scoured the Mediterranean and carried the terror of his name to Sicily, the southern coasts of Italy, Illyricum, and the Peloponnese. He next portioned out the soil of the province of Carthage among his soldiers, and settled the succession. A bigoted Arian in his theology, he persecuted the orthodox Catholics in his dominions with ferocious rapacity and cruelty. The murder of the great Aetius (454), and of his murderer and master Valentinian III., opened up a new field for his ambition. Eudoxia, the widow of Valentinian, eager for revenge upon her husband's murderer Maximus, invited Genseric to Rome. The Vandal fleet reached the mouth of the Tiber in June 455. The wretched Maximus had already fallen, and the city could offer no resistance; all Pope Leo's entreaties did not save it fourteen days of devastating plunder. On leaving the city Genseric carried with him the empress and her two daughters, one of whom became the wife of his son Huneric. The empire twice endeavoured to avenge the indignities it had suffered, but without success. First the Western emperor, Majorian, fitted out a fleet against the Vandals in 457, which was destroyed by Genseric in the bay of Carthage; next, the Eastern emperor, Leo, sent an expedition under the command of Heraclius and others in 468, which was also destroyed off the city of Bona.
Genseric died in 477, in the possession of all his conquests, leaving behind him the reputation of being the greatest of the Vandal kings. His appearance was not imposing: Jordanes describes him as of low stature, and lame on account of a fall from his horse, deep in his designs, taciturn, averse to pleasure, subject to transports of fury, greedy of conquest, and cunning in sowing the seeds of discord among nations, and exciting them against each other. He was ruthless in his cruelty, and seems to have found impulse in the fierce and fanatical bigotry of his religion. Once, when leaving the harbour of Carthage on an expedition, the pilot asked him whether he was going. 'Against all who have incurred the wrath of God,' said the conqueror.