Question about Shock Cavalry in Macedonian and Steppe Armies

[dumuzi]

Hi all!
I'd like to field a question about the development of shock cavalry in Macedonian and steppe armies.
Was there mutual influence between Macedonian hetairoi cavalry and steppe-type shock cavalry? Did the Macedonians adopt shock cavalry from steppe armies (or vice versa)? When is the first recorded example of shock cavalry in steppe-type military expeditions? I am not aware of an example of the Achaemenid Persians using cavalry in this way.
Does anyone think, on the other hand, that these two military traditions were exclusive and had limited influence on one another? Although this is a possibility, I find it noteworthy that shock cavalry was pretty unusual within the military traditions of the Mediterranean world. It was therefore an unusual development.

[QuintusSertorius]

The Makedonian cavalry tradition comes from the Thessalians, it isn't something they invented. Thessaly was a notable exception compared to the rest of Greece, in having a tradition of their elites serving as heavy cavalry, rather than most preferring to fight on foot and cavalry being almost an afterthought.

[dumuzi]

Thanks for the response! That makes a lot of sense.
I didn't know that the Thessalian cavalry tradition was so old. But it makes sense considering the unusual nature of Thessalian society (largely rural landscape dominated by large estates owned by aristocrats, the institutions of penestae and tagoi).
Could you or someone else point me in a good direction for learning up on the cavalry tradition of Thessaly and Macedonia? I read German, Ancient Greek and Latin.
My understanding is that the steppe cavalry would charge at a trotting pace with kontoi lowered as a sort of moving pike hedge. This sort of use of cavalry is mostly effective at breaking already tired and demoralized infantry. For example, the Parthian victory at Carrhae depended on the close coordination between horse archers to wear down Crassus's legions and then a final decisive charge.
I feel like Alexander's cavalry worked in some fundamentally different way. As I understand it, cavalry coordinated with infantry in a sort of early combined arms warfare as opposed to the single decisive charge of e.g. the Parthians at Carrhae.
Do you think this is accurate? It seems interesting to me that you might have two different military/cultural traditions of shock cavalry coexisting in the EB time period and geographic area.

[QuintusSertorius]

I couldn't tell you where exactly I read it, but one of the Thessalian innovations was the use of the wedge and rhomboid formations. They wouldn't sweep the whole enemy formation away as the steppe heavies would, but instead would punch into a formation at a weak spot and go through it like a chisel.