Ever since the time of Alexander and the wars of his successors with each other and their neighbours, it is probable that the supply of captives sold as slaves had been increasing; and in the second century B.C. the little island of Delos had come to be used as a convenient centre for the slave trade. Strabo tells us in a well-known passage that 10,000 slaves might be sold there in a single day.[307] But Rome herself was in the time of Cicero the great emporium for slaves; the wars which were most productive of prisoners had been for long in the centre and the west of the Mediterranean basin. All armies sent out from Rome were accompanied by speculators in this trade, who bought the captives as they were put up to auction after a battle, and then undertook the transport to Rome of all who were suited for employment in Italy or were not bought up in the province which was the seat of war. The enormous number of slaves thus made available, even if we make allowance for the uncertainty of the numbers as they have come down to us, surpasses all belief; we may take a few examples, sufficient to give some idea of a practice which had lasting and lamentable results on Roman society.
After the campaign of Pydna and the overthrow of the Macedonian kingdom, Aemilius Paullus, one of the most humane of Romans, sold into slavery, under orders from the senate, 150,000 free inhabitants of communities in Epirus which had sided with Perseus in the war.[308] After the war with the Cimbri and Teutones, 90,000 of the latter and 60,000 of the former are said to have been sold;[309] and though the numbers may be open to suspicion, as they amount again to 150,000, the fact of an enormous capture is beyond question. Caesar, like Aemilius Paullus one of the most humane of Romans, tells us himself that on a single occasion, the capture of the Aduatuci, he sold 53,000 prisoners on the spot.[310] And of course every war, whether great or small, while it diminished the free population by slaughter, pestilence, or capture, added to the number of slaves. Cicero himself, after his campaign in Cilicia and the capture of the hill stronghold Pindonissus, did of course as all other commanders did; we catch a glimpse of the process in a letter to Atticus: "mancipia venibant Saturnalibus tertiis."[311] It is hardly necessary to point out that we should be getting our historical perspective quite wrong if we allowed ourselves to expect in these cultured Roman generals any sign of compassion for their victims; it was a part of their mental inheritance to look on men who had surrendered as simply booty, the property of the victors; Roman captives would meet with the same fate, and even for them little pity was ever felt. When Caesar in 49 within a few months dismissed two surrendered armies of Roman soldiers, once at Corfinium and again in Spain, he was doubtless acting from motives of policy, but the enslavement of Roman citizens by their fellows would, we may hope, have been repugnant to him, if not to his own soldiers.[312]