Originally Posted by
paulus
Well, there are Greek papyri that securely identify machimoi hippeis in 130 BC settled in the village of Kerkeosiris in the Fayum. They were part of a larger cavalry unit (commanded by Chomenis, of the First Friends and Laarch) dispersed in the Fayum vicinity, and were probably moved to that region from either Upper Egypt or the Delta. There are also demotic Egyptian papyri that give indications of cavalry. About the same time as the cavalry attested at Kerkeosiris, there was a small illegal war between two cities, Hermonthis and Krokodilon Polis, in Upper Egypt. Hermonthis didn't have settlers, and Krokodilon Polis did, although even the settlers at the latter generally were not Greeks. Anyway, the army from Hermonthis included cavalry (they both did, but those from KP were presumably Perses, misthophoroi hippeis), and by deduction they were unlikely to have been much else but machimoi hippeis. Horsemen of Egyptian descent settled at Edfu in Upper Egypt, and Hellenized Egyptians at Panopolis in the northern Thebaid also probably belong in the broadly machimoi hippeis basket.
The machimoi (or at least the Egyptian soldiers, since we don't see a specific terminology in most cases) definitely included cavalry before the Ptolemaic era, and even under Persian rule (for which we don't have a lot of very detailed information) we know of a troop called "the Hyrcanian cavalry" but whose members were actually Egyptians. In the early Ptolemaic era, Ptolemy I put 4,000 cavalry in the field at Gaza, but Ptolemy IV struggled mightily and brought in new recruits to field 5,000 a century later at Raphia. We know that many of the cavalrymen at Raphia were from troops settled well after Gaza, so who were those 4,000 at Gaza? We can't say, but Egyptian cavalry are plausible if we're going to accept that Ptolemy I had anything approaching that number. Then the machimoi hippeis took on a larger role in the dynastic squabbles of the 2nd century, so it's most likely they were there all along. Remember the vast majority of our evidence comes from either incomplete Polybian testimony or a papyrological record focused on the Arsinoite and Herakleopolite nomes, two of the most densely Hellenized regions of Ptolemaic Egypt.