The issue is you cannot train a horse to charge into a wall of men very well, you can train the rider, sure. The olden days spears may have been planted, but not the pikes as they were quite a different weapon, too long. I keep making the point in posts that horsemen without stirrups just cannot do this very well at all, the companions used clever tactics to demoralise and flank and were an exception. Horse normally went horse There is some cases where charging a huge wall of spears forced the horses in as there was nowhere else to go to the horses would halt. Dodgy stuff and often down to whether the spearmen broke before impact. Various professional foot armies soon got the hang of the fact that if you left gaps the horses would plogh through those so it was quite dangerous for horse and when the square arrived they really had no hope without artillery to make a few holes. The point I am making is it is more the training of the foot than the training of the cavalry, hence why scythed chariots only really worked once, Archelaus was a lucky general on the day.