s in between. He characterizes each group:
Nomads are rough, savage and uncultured, and their presence is always inimical to civilization; however, they are hardy, frugal, uncorrupt in morals, freedom-loving and self-reliant, and so make excellent fighters. In addition, they have a strong sense of ‘asabiya, which can be translated as ‘group cohesion’ or ‘social solidarity’. This greatly enhances their military potential. Towns, by contrast, are the seats of the crafts, the sciences, the arts and culture. Yet luxury corrupts them, and as a result they become a liability to the state, like women and children who need to be protected. Solidarity is completely relaxed and the arts of defending oneself and of attacking the enemy are forgotten, so they are no match for conquering nomads. 
With regard to the political and social cycle, Ibn Khaldun suggests the following sequence of events:
Nomads conquer territories and their leaders establish a new dynasty. At first the new rulers retain their tribal virtues and solidarity, but soon they seek to concentrate all authority in their own hands. Increasingly they rule through a bureaucracy of clients - often foreigners. As their former supporters lose their military virtues there is an increasing use of mercenaries, and soldiers come to be more important than civilians. Luxury corrupts ethical life, and the population decreases. Rising expenditure demands higher taxes, which discourage production and eventually result in lower revenues. The ruler and his clients become isolated from the groups that originally brought them to power. Such a process of decline is taken to last three generations, or about one hundred and twenty years. Religion can influence the nature of such a model; when ‘asabiya is reinforced by religion its strength is multiplied, and great empires can be founded. Religion can also reinforce the cohesion of an established state. Yet the endless cycle of flowering and decay shows no evolution or progress except for that from the primitive to civilized society. 
Ibn Khaldun acknowledges that there are turning points in history. He wrote that in his time, he believed the Black Death and Mongol invasions were turning points, as was the development of Europe.
Ibn Khaldun's observations and research focused on the etiology of civilizational decline, “the symptoms and the nature of the ills from which civilizations die.” 
Ibn Khaldun's thesis, that the conquered race will always emulate the conqueror in every way,  and his theory about asbyiah (group feeling / party spirit) and the role it plays in Bedouin societies is insightful. The genius of this work is his study of the science of human culture, the rise and fall of empires, Ibn Khaldun termed this the science of umran (civilization), and it contains many pearls of wisdom. His “Introduction” is his greatest legacy, left for all of humanity and generations to come.
L. E. Goodman prepared a comparative study of Thucydides, who is considered the ‘father of history’, and the Muqaddimah. Goodman reveals the similarities in methods, assumptions, and conclusions, and notes that
Both men are naturalists, both empiricists, both exponents of a critical approach to historiography. Yet neither is a reductionist. Both seek a lesson in history, and both believe that the message of history is to be discovered in the careful study of historical laws revealed in the play of forces which are the expression of man's political and social nature. But beyond similarities of approach, there is a deep congruity of thought between the two authors, for both believe themselves to have glimpsed the pattern, learned the lesson of history. Both Ibn Khaldun and Thucydides have been led by their study of history to a cyclical, rather than linear view of historical process; both have been led, in developing their concepts of human and political reality, to a qualified relativism, which affords them … a cautious but by no means pessimistic historical theodicy. 
Although Goodman finds similarities between some of the historical theories of the two hist