Dr. @BretDevereaux covers the effectiveness of horse-borne nomads here:
https://acoup.blog/2020/02/28/collections-the-fremen-mirage-part-iv-desert-power/ …
He notes that there was something particularly effective about pastorialist *methods* of warfare (enabled by their way of life), rather than their lifestyles making them extra tough.
I certainly had more to say on Ibn Khaldun, but the context of a blog post that is fundamentally about the modern reception of a Greek and Roman (and not Arab) literary topos (filtered through later Europe), I thought 1,800 words on Ibn Khaldun was about as much as I could afford