Bear in mind that Wikipedia is a vanity message board for Harvard alumni, and therefore guaranteed to report with a straight face anything that praises enemies of liberty.

That period is when Islam had a stranglehold on progress. No knowledge or goods could be exchanged without paying protection money. It is during this period that the great "Islamic contributions" were brought to the West, such as the numerical system they took from India, the medical texts that were at Alexandria before their burning of the Library since the other books were not the Koran, and the abstract designs that arose from the execution for heresy of anyone who attempted to depict a real object. This was possible because of the increased prosperity of the local bandits as they shook down traders; it gave them the resources to indulge their mutual treachery, breaking down unified authority. (Centralized power over thought is always toxic to the pursuit of knowledge; look at Galileo, or what the Algorean cult is trying to do to Freeman Dyson).

I never heard Poitiers described as a highwater mark; it was a turning point in which the war with barbarism began being won.

And to be fair, what you and I think of as a nation-state didn't really exist before 1648.