I think you mean they preserved Greek and Roman knowledge, which was the basis of the Renaissance. The Enlightenment was a few hundred years later, and consisted of new ideas.

They didn’t just preserve Greek and Roman knowledge. Averroes, Avicenna, the Mutazilites, al-Razi, Maimonides, al-Farabi and others made enormous and original contributions to philosophy, medicine, chemistry and other fields. The Renaissance and the Enlightenment would have been unrecognizably different without the contributions of the thinkers of the Islamic world.

Can you suggest some reading materials to those who want to know more about this?

My knowledge of this period is very shallow and mostly comes from the History of Phiosophy Without Any Gaps podcast. Lost Enlightenment is probably the best place to start.

https://www.amazon.com/exec/obidos/ASIN/B00F8MIJMQ/geneexpre...

The Enlightenment was something new under the sun. The Islamic Golden Age was intellectually impressive but nothing in it presages the ideas of individualism and freedom that are at the heart of the Enlightenment project.

The heart of the Enlightenment project is the realization that educated, non-poor citizens are more effective at waging war with other countries.

That’s not an accurate description of the military revolution that began with Revolutionary France and the levée en masse or of the Prussian General Staff system, the two major military organizational innovations of the Enlightenment era. Prussia and France both had mass armies but neither was terribly well educated, officers aside, and calling Prussian subjects citizens is misleading in the extreme. It suggests participation in political life that was restricted to a tiny segment of the population.