The state is suffering from two opposite vices, avarice and luxury; two plagues which, in the past, have been the ruin of every great empire.
[Titus Livius，From the Founding of the City]

Un empire fondé par les armes a besoin de se soutenir par les armes.
[Montesquieu，Considérations sur les causes de la grandeur des Romains et de leur décadence]

It was scarcely possible that the eyes of contemporaries should discover in the public felicity the latent causes of decay and corruption. This long peace, and the uniform government of the Romans, introduced a slow and secret poison into the vitals of the empire. The minds of men were gradually reduced to the same level, the fire of genius was extinguished, and even the military spirit evaporated.
[Edward Gibbon, The History of the Decline and Fall of the Roman Empire]