Great Samizdata post on the Fall of the Roman Empire.

Contrary to myth, the empire did not collapse in the face of unstoppable barbarian hordes. The numbers of barbarians were always small (a mere 80,000 vandals took the whole of Roman Africa in less than a decade). The empire fell because many of its citizens had emigrated to the freer, more pleasant barbarian lands (under the late empire, the population fell from 70 to 50 million) and, crucially, the invading barbarians found themselves welcomed as armies of liberation by vast numbers of oppressed people. The empire had been warned. In De Rebus Bellicus, published anonymously around AD 370, the author called for tax cuts, new technology, and political freedoms: 'In the technical arts, progress is due not to those of the highest birth or immense wealth or public office or eloquence derived from literary studies but solely to men of intellectual power . . . [the barbarians] are by no means considered strangers to mechanical inventiveness.' The author blamed the greed of the rulers for the desperation of the poor: 'This store of gold meant that the houses of the powerful were crammed full and their splendour enhanced to the destruction of the poor, the poorer classes of course being held down by force. But the poor were driven by their afflictions into various criminal enterprises, and losing sight of all respect for the law, all feeling of loyalty, they entrusted their revenge to crime. For they often inflicted the most severe injuries on the Empire, laying waste the fields, breaking the peace with outbursts of brigandage, stirring up animosities, and passing from one crime to another, supported usurpers.' Unfortunately, this very sensible tract was never shown to the Emperor, Valentinian I, even though Ammianus Marcellinus tells us that he was one of the emperors who actually was interested in inventions.