During the post-Roman, pre-Medieval and Early Medieval periods the Cataphract, or Kataphraktoi, was the most disciplined, heavily armoured and effective cavalry unit known to man. Even in the High Medieval and Late Medieval periods, these fearsome cavalry remained to be of the strongest cavalry, and were only outdated after the Medieval period.

Kataphraktoi were used in the Byzantine Empire's army. Compared to Western Knights, these cavalry were veritable tanks. They wore incredibly heavy armour, so heavy that even the counter-cavalry weapons such as Halberds, Pikes, Guisarmes etc. had trouble getting through their armour. Their horses weren't run of the mill either, but rather carefully bred over the centuries into the perfect Arabian horses, well trained to carry such extreme weight at speeds that were considered fast for such heavy armour.

The Kataphraktoi riders themselves were similarly elite. They were trained over many years, and there were not many of them. In relation to the West, the Knights of the Templar, Knights of the Round Table, Knights of Santiago etc. were carefully trained orders such as the Kataphraktoi. They were elite guards used to guard royalty on the battlefield, and generally anywhere where the Vanguard Elite were unable to guard the given royalty.

Thus, on the battlefield they weren't all too common, and they weren't generally deployed on the field without any royalty to accompany them, but when they were on the field they were incredibly effective. Their speed matched most Western mid-heavy cavalry, and it definently exceeded the speed of their heavier knights, yet, as mentioned earlier, they had terribly thick armour. When faced with bows and crossbows, the Kataphraktoi could virtually charge through, slicing any archers foolish enough to get in the way of their short swords, and to any that were caught by the charge, they were crushed by the heavy hooves. Not many survived.

Against other cavalry they were also quite effective. Heavy Knights were slower, and thus could be flanked and defeated by the heavier armour, mid-heavy cavalry could generally be caught and defeated, and any medium or light armoured cavalry that did attempt to engage them generally didn't survive long against their thick armour and discipline.

Most cavalry found that against infantry, especially the above mentioned counter-cavalry, they were, as expected, decimated. Kataphraktoi, however, found themselves in a much better position. Their thick armour made it hard to get through, and their discpipline and training meant they knew when and how to strike. All but the most heavily trained infantry fell beneath the Kataphraktoi.

Yet it was not simply training and armour that made them such a fearsome tool, it was the morale they induced. As it usually accompanied royalty, it instilled positive morale in friendly troops, and even the reputation of the Kataphraktoi instilled this morale. Similarly, this instilled negative morale in the enemy, and the sound of the thundering hooves caused by the weight of the armour also caused negative morale. Thus, the Kataphraktoi was a highly effective cavalry, lasting over 600 years.