THE BARBARIAN INVASIONS 83 tecture. It is in the shape of a Latin cross with a low tower rising over the crossing. Within this tower is a dome cov- ered, like the arched ceilings of the arms of the cross, with beautiful mosaics in blue and gold. In the three short arms rest the empty sarcophagi of the emperors, Constantius III and Valentinian III, and the empress, Galla Placidia. Meanwhile the barbarians had been continuing their invasions. The Vandals, who remained in Spain after the West Goths had returned to Gaul, moved south- The ward and by 425 were attacking the African Vandals coast. In 429 they began a wholesale invasion of Roman North Africa under their new king, Gaiseric, who was to have a long reign until 477. A civil war between Boniface, Count of Africa, and the court at Ravenna afforded them a good opening. Boniface and Ravenna soon reunited against them and an army was also sent from Constantinople, but to no avail. The Vandals, however, found the taking of walled towns slow work, especially as they were accustomed to fight on horseback; and in 435 they made a peace by which they were to hold Mauretania and part of Numidia as tributary allies of Rome. But the Vandals had by this time built up a navy of small, swift vessels which soon gained the Balearic Islands, Sardinia, and part of Sicily, and committed acts of piracy all over the Mediterranean. Thus the Empire became everywhere infested with barbarians, by sea as well as by land. In 439 Gaiseric pounced unexpectedly upon Carthage. A fleet which the Eastern emperor sent to the rescue accomplished little, and in 442 the Western emperor came to terms with the Vandal and recognized his complete independence. Gaiseric, however, dated the beginning of his reign and also of the legal year from the day when he captured Carthage. When Valentinian III was assassinated in 455, Gaiseric sailed to Italy, took Rome without resistance, sacked it for two weeks, and carried off the imperial widow and her two daughters. In Gaul during the reign of Valentinian III the chief representative of the Empire was Aetius, a statesman and
