Montesquieu published a book called Considerations in 1734 on the causes of the greatness of the Romans and their decline.  This book covers the period from early monarchial and republican Rome through the empire.  It also covers the overrunning of the western empire by barbarians in the 5th century and the collapse of the eastern empire.  It praises the virtues amid liberty of the republic and deminstrates that its very success in war led to corruption of its institutions and establishment of imperial despotism.

Considerations acknowledged the disasters that conquest brought on the conqured peoples.  It also examines the forces within the empire that caused its weakening long before the depredations.  It also shows that the eastern empire serves as an illustration of the improper relation of religion to political society and it was torn with Christian strife. 

The book also uses reflections on human nature and foundations of political life to elucidate those matters.  It contends its general moral and physical causes rather than particular accidental causes that rule the affairs of men.  It prescribes to the individual the degree of their freedom.