Hard riding no saddles or stirrups

[Chuck Russell]

The actual, specific meaning of a cavalry charge is really a very difficult problem to solve. There is no longer any legal context to treat horses and men in this manner. Literary sources, unless they are instructional, are not so good because people use metaphors and things. So when someone says, such and such cavalry 'smashed into the rear of the enemy line' you don't really know what that means. In fact, I don't even know if we know what it means in Neopoleanic times much less Roman times. I bet there's some very good information from Napoleon's time period regarding what horses will do and not do. It may be an easier place to start to find useful information about ancient cavalry. It's an area of military history that could use some serious study, because our grip on it is rapidly fading from memory. Did Napoleon's cavalry officers need to read any 'how to' books?

If soccer team A 'kicks the butt of' soccer team B, one might get strange ideas regarding the rules of soccer a thousand years on.

That would indeed be a good place to start.
First of all, horses cannot be made to charge into a closed body of men, though they do charge single men. Napoleonic infantry formed square when attacked by cavalry. Against a closed square of bayonets cavalry is impotent. There is only one instance known of a square broken by cavalry. What happened however is that a wounded horse fell upon the infantrymen in front of him and in thrashing about created a gap through which the cavalry could enter the square and disperse it. Of course this only proves the point.
Secondly when two bodies of cavalry charge each other interesting things happen. Normally it workes out as a game of chicken. One side loses its nerve and takes flight before the troops actually meet. From the Napoleonic eary there is an eyewitness description of a charge where the lines opened up before impact and the riders passed each other with some swordplay, the lines reformed at opposite ends and the troops disappeared from sight.

ummm they did up the hill at hastings did they not? 3 times even they charged at a line of saxons.