N.B.: The above mechanism won't allow to see calculated combat information modified by leadership, unless the leader is already there.

If you want to make also this information easily available, I would suggest the following:
- If the player has this option (I'll call it "Mouseover combat information/calculations") set to "on",
- allow the player to right-click on "Unit B", and add to the context menu three items: "Combat info with 1/2/3 level(s) of leadership". (Having four levels is possible, so if really wanted, make that four menu items.)

- OR: Make that a toggle in the context menu, that can be set to exactly one option between 0 and 4 levels of leadership, after which all the mouseover combat information tips will show the combat data with the appropriate modifications.

a.k.a. Provide a way to see combat information when not able to attack

I’m going to record a long-discussed and long-needed feature request that re-emerged on wesnoth-dev mailing lists in april, so that it may get remembered. I will record this in two parts, as it is up to the implementation whether fixing one request also fixes another. My suggested mechanism below would allow to address the issue with both requests.

Part 1. When you can not directly attack a unit, you can not see the combat information (damage, number of attacks, CTH, etc.). However, the information should be available to the player without needing to manually calculate it.

Part 2a. Often, you would like to know the combat information the other way around, i.e. “how much damage can they do to my leader, on their next turn, if I move my leader there”, or (my pet example), “if my horseman (charge) misses that orcish archer, how much damage will he (ranged) do to my horseman next turn (when it is dusk)”. In this case also, the information exists (and is no secret), but currently you are forced to do the math manually.
Part 2b. Or, you'd like to know what damage your ally can do, on their next turn.

On the mailing list, Jetryl suggested a mouseover solution for showing combat information, which sounds extremely practical. Ott concluded that: “This sounds like a really useful idea for advanced/serious players. It should probably be possible to switch this off as a preference, though, and the default setting perhaps should be ‘off’.”

My envisioned solution sets off with Jetryl’s idea of a mouseover “tooltip” (or should I say “combat tip”).
- 1: select a unit (Unit A) by clicking on it. This can be any unit, opponent, ally, or own.
- 2: mouseover another unit (Unit B). Unit A doesn’t need to be able to attack Unit B. For all we care, they can be on the opposite sides of the map.
- 3a: if Unit A is your own, bling, a “tooltip” showing the essential combat information shows up.
- 3b: if the first unit, i.e. Unit A, is an enemy (or an ally), the game should first take into account the time of the day on Unit A’s next turn, and show the combat information with the appropriate ToD bonus.

- 4: to reduce screen noise (and the need for the computer to perform combat calculations), the feature can be programmed with an additional constraint such that if both affected units are on the same side, combat information will not be shown. This will allow to prevent frustration when choosing a unit and then moving through lines of friendly units, in that the game will not try to give you information on what would happen if Konrad tried to attack Delfador. :-)

Please see the following messages in the abovementioned wesnoth-dev -thread for reference:
https://mail.gna.org/public/wesnoth-dev/2006-04/msg00050.html
https://mail.gna.org/public/wesnoth-dev/2006-04/msg00058.html
https://mail.gna.org/public/wesnoth-dev/2006-04/msg00059.html