After the high culture, follows the civilization phase of social upheavals, mass movements of people, constant war and crisis, and the growth of the megalopolis.

Oswald Spengler : Author
The "civilization" phase witnesses drastic social upheavals, mass movements of peoples, continual wars and constant crises. All this takes place along with the growth of the great "megalopolis" -- huge urban and suburban centers that sap the surrounding countrysides of their vitality, intellect, strength, and soul. The inhabitants of these urban conglomerations -- now the bulk of the populace -- are a rootless, soulless, godless, and materialistic mass, who love nothing more than their panem et circenses. From these come the subhuman "fellaheen" -- fitting participants in the dying-out of a culture.

Spengler, Oswald. The Decline of the West (Vol. 1, "Form and Actuality"; Vol. 2, "Perspectives of World History"). New York: Alfred A. Knopf, 1926 and 1928.