Decadence is not physical, Glubb argues:
The citizens of nations in decline are sometimes described as too physically emasculated to be able to bear hardship or make great efforts. This does not seem to be a true picture. Citizens of great nations in decadence are normally physically larger and stronger than those of their barbarian invaders.
Moreover, as was proved in Britain in the First World War, young men brought up in luxury and wealth found little difficulty in accustoming themselves to life in the front-line trenches. The history of exploration proves the same point. Men accustomed to comfortable living in homes in Europe or America were able to show as much endurance as the natives in riding camels across the desert or in hacking their way through tropical forests.
Decadence is a moral and spiritual disease, resulting from too long a period of wealth and power, producing cynicism, decline of religion, pessimism and frivolity. The citizens of such a nation will no longer make an effort to save themselves, because they are not convinced that anything in life is worth saving.