I realised I had done this post all wrong - mounted vs mounted charge and melee combat are resolved twice, reflecting the speed with which mounted fighting is concluded compared to infantry fighting.
So here goes again....
Cavalry vs cavalry combat is more fluid than infantry vs infantry since all cavalry types with the exception of really cumbersome heavies like cataphracts can evade a charge and also break off after melee combat.
A Roman medium cavalry unit faces off against Spanish light horse. LH morale is generally lower than MC, reflecting the LH's more brittle morale when engaged in hand-to-hand fighting (which it preferred to avoid if possible). The MC draws charge combat against the LH but wins melee. The LH however can outshoot the MC, scoring 2 shooting hits for the MC's 1. Who wins the fight? Answer is, it depends. Here are three combats: in the first the MC general has a better combat rating than the LH general (combat rating is the number in the grey square on the general's counter). In the second both generals' combat ratings are equal, and in the third the LH's general has the better combat rating.
An Optio battlefield is typically 8 squares deep though that can vary according to the scenario. I use 8 squares here.
FIRST FIGHT
In all three fights the LH have moved up to the MC to gain as much depth behind them as possible. Here the Roman general has a better combat rating than the Spanish general.
Turn 1. Spain.
The LH move up and trade javelins with the MC at a ratio of 2:1. Shooting hits are indicated by small arrows. The first arrow is green, second is yellow, third is orange and fourth is red. When the fourth arrow is reached the unit suffers a loss of one morale interval, i.e. a shooting hit is equivalent to ¼ of a morale hit. Units can shoot during their and their opponent's move, i.e. twice in a turn, at any moment during either player's move. After the red arrow the next shooting hit turns the dial to green arrow and so on.
Turn 1. Rome.
The Roman MC charges, collects two more shooting hits and drops a morale. A charging unit cannot itself shoot.
The LH then evade, rotating 180 degrees, pulling back far enough so the MC cannot reach them - 3 squares in this case - and then (optionally) rotating 180 degrees again. Agile class units like cavalry can rotate 180 degrees twice in a move. Light infantry like skirmishers and peltasts can also do it. The MC follow up.
Turn 2. Spain.
Evaded units cannot move or shoot in their turn after their evade (they have used up their normal move in their evade move). The MC however can donate a few javelins to them.
Turn 2. Rome.
The Romans charge again and collect their two missile hits from the Spanish (that green arrow should be yellow BTW)....
....who cannot evade this time since that would see them quit the battlefield. They must take it on the chin like men. Charge combat between MC and LH is normally drawn, but in this case the Roman general can break the tie and add an extra combat hit. Mounted vs mounted combat is resolved twice, but a general or commander's bonus is applied only once to the first round of combat, which means the LC lose the first round and draw the second, dropping one morale interval in total.
Turn 2. Melee.
In melee combat MC score 3 hits against LC who score 2 hits back. Generals and commanders help in melee only by raising the highest shaken interval (the white squares) to firm, so in this case the LH lose two morale intervals and rout.
Conclusion: LH facing MC who have a better general in the open stand no chance unless they have plenty of space behind them and can shoot and evade indefinitely. Fine if you're a Mongol but in a set piece battle that rather negates your role as infantry support. You have to do something to equalise the situation.
I'm just dashing off on a family visit. I'll do the next two examples soon.
SECOND FIGHT
Here the two generals have the same combat rating.
Turn 1. Spain.
The Spanish LH move up and javelins whizz through the air.
Turn 1. Rome.
The Romans charge and collect their shooting hits and morale loss.
The LH evades, followed by the MC.
Turn 2. Spain.
The evaded LH can't do anything except receive a few javelins from the MC. At the end of the turn they revert to normal.
Turn 2. Rome.
The Roman cavalry charge and again become a hedgehog in reverse.
This time the LH can't evade without leaving the battlefield so stay to fight it out. With both generals having the same combat rating the charge combat is drawn and neither unit loses morale. The generals aren't injured either.
Turn 2. Melee.
MC score 3 combat hits against LH in melee who score 2 hits back, so the LH lose 1 morale - twice as melee is resolved twice. A bit of good news for the Spanish: the Roman general is wounded.
After melee combat the LH breaks off. All agile units can do this.
Turn 3. Spain.
The LH stays where it is. If it moves up to shoot the MC it will shoot at a -1 modifier since it is shaken. This means it will get as many shooting hits as it gives and it will take only two more shooting hits to drop it another morale interval and rout it. What to do? What to do?
Turn 3. Rome.
The Romans charge in, collecting one missile hit from the shaken LH.
The charge slams home. The LH general boosts its shaken interval to firm and the fight is a draw, with neither unit losing morale.
Turn 3. Melee.
And then it's all over. The LH are outfought in melee and rout.
Conclusion: LH can't stand against MC in a straight fight with both generals equal in combat ability.
THIRD FIGHT
The LH general has a better combat rating than his MC opponent. Before reading through to the end, who do you think wins the fight?
Turn 1. Spain.
Up come the Spanish and there is a rapid two-way traffic flow of javelins.
Turn 1. Rome.
The MC charges and, well, we know what happens.
The LH evade in the good old skirmisher cavalry fashion.
Turn 2. Spain.
The evaded LH do nothing whilst the MC chuck some javelins their way.
Turn 2. Rome.
The MC charges and gets its donation of javelins, dropping a morale.
The LH can't evade any further so the charge slams home. Charge combat is resolved twice but generals can apply their modifiers only once. The first round of combat is a draw, so the LH general, having a better combat rating than the MC general, breaks the tie and adds a combat hit, inflicting one morale loss on the MC and dropping it to shaken. In the second round of combat the MC, now shaken with a -1 modifier, loses the fight and drops another morale interval. All is going well for the LH but their general is wounded.
Turn 2. Melee.
Not that it matters. The shaken MC again fight at a -1 meaning the fight is drawn and both sides lose a morale. The MC general can't help as he can boost only the highest shaken interval to firm. The MC rout.
Conclusion: with a better commander the LH can handily outfight the MC. So generals are important.
Bonus feature: What about terrain? Does that change things?
FOURTH FIGHT
This time LH use scattered woodland to their advantage. Scattered woodland doesn't slow LH down but it does slow MC down from 3 squares per move to 2. The LH general is inferior to the MC general. So it should be a walkover for the MC. Right?
Turn 1. Spain.
The LH move up into the scattered woodland and shoot the MC. Scattered woodland doesn't affect anyone shooting out of it, but does inflict a -1 modifier to anyone shooting into it. In this case the MC's shooting factor of 1 drops to ½. That means that the MC can shoot only during the LH's move, i.e. only once per turn instead of the usual twice. It's the LC's move here, so the MC can hand them javelins pointy end first.
Turn 1. Rome.
The Romans charge and we know what happens.
The MC evade but this time fall back only 2 squares as the MC can pursue only 2 squares. The LH are in another scattered woodland square and the MC are in the open. Beginning to get the picture?
Turn 2. Spain.
The MC shoot the LH for another shooting interval.
Turn 2. Rome.
The MC charge and collect 2 more shooting hits.
The LH evade back another two squares, pursued by the MC.
Turn 3. Spain.
The evaded LH collect another spat of javelins.
Turn 3. Rome.
The Romans charge, are shot to red and drop another morale. They are now shaken.
Turn 3. Melee.
The MC are shaken but their general boosts the shaken interval back to firm and they win the first round of combat against the LH who drop a morale interval. For the second round however the general doesn't influence the fight (he applies his combat rating only once) and with a -1 modifier on the MC the fight is a draw and both sides lose a morale interval.
At this point the LH, after carefully considering the situation, decide to break off.
Turn 4. Spain.
The LH come back, this time to shoot the MC. Since they are shaken they score only one shooting hit on the MC, but the MC, with a -1 for shaken and another -1 for shooting into scattered woodland, score no hits at all.
Turn 4. Rome.
The Roman cavalry charge, collecting another shooting hit.
Turn 4. Melee.
And it's finally all up for the LH. the charge is a draw but the MC general, with a superior combat rating, breaks the tie and routs the LH.
Conclusion: terrain makes a difference but there are no wunderwaffen in Optio.
Second conclusion: if the Spanish general had been as good as the Roman one, the Spanish would have drawn the charge and won the melee, routing the Romans.
