I am writing a thesis. What are the causes of the rise and fall of nations?

Answer

The causes for the rise and fall of nations are different for Muslims and non-Muslims. While non-Muslims progress and gain political power by concentrating on and harnessing the material forces regardless of whether they degenerate to the levels of satanism morally. In this temporary phase of existence, namely, life on earth, non-Muslims progress in proportion to their worldly efforts.

On the contrary, the rise of the Muslim nation (the Ummah) is dependent entirely on moral reformation and spiritual elevation in the light of the Qur'aan and Sunnah. This was the secret of the rapid progress of the early Muslims who had conquered half the known world of the time within the span of a generation. The Qur'aan and Hadith state explicitly that power on earth for Muslims is reliant on obedience to Allah Ta'ala.

"Inheriting the earth" and the "dominion of the earth" refer to political power, and this is dependent on total obedience to the Shariah and the Sunnah. These divine promises were fulfilled during the era of the Sahaabah and the immediate eras after them. However, when Muslims lost themselves in worldly and carnal pursuits and pleasures, the decline set in until it reached the stage of utter ruin and humiliation for Muslims. And, this ruin and humiliation are incremental because Muslims have failed to understand the causes of their decline and degradation.

With total obedience to Allah Ta'ala comes total 'dominion', that is control of and ascendency in all aspects of life, both mundane and spiritual.