Nicene and Post-Nicene Fathers, Vol. II:
City of God: Chapter 7

Chapter 7.—Whether Earthly Kingdoms in Their Rise and Fall Have Been Either Aided or Deserted by the Help of the Gods.

If this kingdom was so great and lasting without the aid of the gods, why is the ample territory and long duration of the Roman empire to be ascribed to the Roman gods?  For whatever is the cause in it, the same is in the other also.  But if they contend that the prosperity of the other also is to be attributed to the aid of the gods, I ask of which?  For the other nations whom Ninus overcame, did not then worship other gods.  Or if the Assyrians had gods of their own, who, so to speak, were more skillful workmen in the construction and preservation of the empire, whether are they dead, since they themselves have also lost the empire; or, having been defrauded of their pay, or promised a greater, have they chosen rather to go over to the Medes, and from them again to the Persians, because Cyrus invited them, and promised them something still more advantageous?  This nation, indeed, since the time of the kingdom of Alexander the Macedonian, which was as brief in duration as it was great in extent, has preserved its own empire, and at this day occupies no small territories in the East.  If this is so, then either the gods are unfaithful, who desert their own and go over to their enemies, which Camillus, who was but a man, did not do, when, being victor and subduer of a most hostile state, although he had felt that Rome, for whom he had done so much, was ungrateful, yet afterwards, forgetting the injury and remembering his native land, he freed her again from the Gauls; or they are not so strong as gods ought to be, since they can be overcome by human skill or strength.  Or if, when they carry on war among themselves, the gods are not overcome by men, but some gods who are peculiar to certain cities are p. 68 perchance overcome by other gods, it follows that they have quarrels among themselves which they uphold, each for his own part.  Therefore a city ought not to worship its own gods, but rather others who aid their own worshippers.  Finally, whatever may have been the case as to this change of sides, or flight, or migration, or failure in battle on the part of the gods, the name of Christ had not yet been proclaimed in those parts of the earth when these kingdoms were lost and transferred through great destructions in war.  For if, after more than twelve hundred years, when the kingdom was taken away from the Assyrians, the Christian religion had there already preached another eternal kingdom, and put a stop to the sacrilegious worship of false gods, what else would the foolish men of that nation have said, but that the kingdom which had been so long preserved, could be lost for no other cause than the desertion of their own religions and the reception of Christianity?  In which foolish speech that might have been uttered, let those we speak of observe their own likeness, and blush, if there is any sense of shame in them, because they have uttered similar complaints; although the Roman empire is afflicted rather than changed,—a thing which has befallen it in other times also, before the name of Christ was heard, and it has been restored after such affliction,—a thing which even in these times is not to be despaired of.  For who knows the will of God concerning this matter?