heavy cavalry engaging heavy cavalry

[Michael Kerr]

Urselius wrote:

A slow attack could be delivered in a tight and regular formation, a charge at speed, a la outrance, unavoidably led to an opening of ranks as individual horses differed in their top speed.

While I agree with you about ranks opening up at speed, in regard to cataphracts, I think that their strength lay in maintaining a tight & disciplined formation when attacking lighter cavalry with maybe lots of wheeling & turning to isolate & destroy enemy cavalry & as Peter pointed out this comes through training, both horse & rider. Because of their heavier armour & bigger horses, the light cavalry of the enemy with their swifter & lighter horses could more than likely evade an individual cataphract's charge & attack him from another angle or in groups (unless they had the lighter cavalry pinned against a natural obstacle like a river, or caught them totally unawares.)
However, as someone pointed out in an earlier post things can go wrong with a tight formation attacking at speed when the lead horses lose momentum or face an obstacle. In 484AD the Hephthalites using feigned retreat tactics lured Sassanid Savaran heavy cavalry to a prepared ditch measuring (from book Shadows in the Desert by Dr Kaveh Farrokh) 30 feet wide & 60 feet long camouflaged with wood, soil, shrubs & foliage and probably in a narrow valley, placing their horse archers in front of ditch to lure Savaran to attack & then crossed the ditch through a safe pre designated passage over the hidden trap with Savaran in full pursuit. Peroz & most of Savaran plunged into the ditch as well as a lot of support cavalry but momentum had stopped & the riders & horses who managed to avoid the ditch were easy targets for the Hephthalite horse archers. The size of the ditch indicates that Savaran were pursuing in a reasonably tight or wedge formation & the carnage inflicted on the Savaran by the trap seems to indicate that they were attacking at speed.

Regards
Michael Kerr