Hi David,
I have not legislated for unformed infantry to fight back against cavalry, they basically just stand and take it.
If you think about the mechanism for Cavalry charging formed infantry...
1. CAVALRY DECLARE CHARGE - and test to succeed
2. INFANTRY TEST to receive
3. If they don't retreat or rout they then test for STAND AND FIRE effect distance.
4. They FIRE(this is their chance to stop the cavalry or do enough casualties to make the overall melee result a win for them)
5. If hit, CAVALRY TEST TO CHARGE HOME (Fail =rout, pass means contact)
5. Cavalry dice to kill infantry hoping that they inflict more than they receive to get a win. Equal is a draw with a second round and no pushbacks. Lose(for the infantry is a pushback and test.. break if RAW)
So infantry's `fight back' so to speak, is in their volley as the cavalry charge, no other fighting back against cavalry allowed