Despite this grave danger, or perhaps because of it, the Roman army continued to be wracked by usurpation, in one of which Stilicho, Rome's foremost defender of the period, was put to death. It is in this climate that, despite his earlier setback, Alaric returned again in 410 AD and managed to sack Rome.Matyszak, The Enemies of Rome, p. 267 The Roman capital had by this time moved to the Italian city of Ravenna, but some historians view 410 AD as an alternative date for the true fall of the Roman Empire. Without possession of Rome or many of its former provinces, and increasingly Germanic in nature, the Roman Empire after 410 AD had little in common with the earlier Empire. By 410 AD, Britain had been mostly denuded of Roman troops,Churchill, A History of the English-Speaking Peoples, p. 16 and by 425 AD was no longer part of the Empire, and much of western Europe was beset "by all kinds of calamities and disasters", coming under barbarian kingdoms ruled by Vandals, Suebians, Visigoths and Burgundians. The remainder of Rome's territory—if not its nature—was defended for several decades following 410 AD largely by Flavius Aëtius, who managed to play off each of Rome's barbarian invaders against one another. In 435 AD he led a Hunnic army against the Visigoths at the Battle of Arles, and again in 436 AD at the Battle of Narbonne. In 451 AD he led a combined army, including his former enemy the Visigoths, against the Huns at the Battle of the Catalaunian Plains,Gibbon, The Decline and Fall of the Roman Empire, p. 489 where Aëtius managed to halt the Hunnic onslaught. However, Concordia, Altinum, Mediolanum, Ticinum, and Patavium were sacked, and the Huns returned a year later. After brutally razing Aquileia, the Huns continued to move towards Rome. It was at this point that Pope Leo I managed to convince Attila to leave. Despite being the only clear champion of the Empire at this point, Aëtius was slain by the Emperor Valentinian III's own hand 2 years afterwards, leading Sidonius Apollinaris to observe, "I am ignorant, sir, of your motives or provocations; I only know that you have acted like a man who has cut off his right hand with his left". Carthage, the second largest city in the empire, was lost along with much of North Africa in 439 AD to the Vandals,Procopius, History