If the Roman conquest did not altogether put an end to these sentiments, it considerably mitigated their intensity. The imperial city was too strong to feel endangered by the introduction of alien deities within its precincts. The subject states were relieved from anxiety with regard to a political independence which they had irrecoverably lost. Moreover, since the conquests of Alexander, vast aggregations of human beings had come into existence, to which the ancient exclusiveness was unknown, because they never had been cities at all in the ancient sense of the word. Such were Alexandria and Antioch, and these speedily became centres of religious syncretism. Rome herself, in becoming the capital of an immense empire, acquired the same cosmopolitan character. Her population consisted for the most part of emancipated slaves, and of adventurers from all parts of the world, many of whom had brought their national faiths with them, while all were ready to embrace any new faith which had superior attractions to offer. Another important agent in the diffusion and propagation of new religions was the army. The legions constituted a sort of migratory city, recruited from all parts of the empire, and moving over its whole extent. The dangers of a military life combined with its authoritative ideas are highly favourable to devotion; and the soldiers could readily adopt new modes for the expression of this feeling both from each other and from the inhabitants of the countries where they were stationed, and would in turn become missionaries for their dissemination over the most distant regions. That such was actually the case is proved by numerous religious inscriptions found in the neighbourhood of Roman camps.[313]