Information transfer?

Combat on Horseback seems to be the larger page. I think Mounted Combat should become an alias for that.

What's more important here is not which page is the "largest", but which page is more descriptive of the concept itself.  In my opinion Mounted Combat is a much better description.

Bumping. Any other thoughts?

I agree with MB. Mounted Combat seems more useful, for instance the level in Turok 2 where the player rides a dinosaur.

It should just be Mounted Combat because combat on horseback is mounted combat.

Combat on Horseback is specific to fighting while riding a horse.
 
Mounted Combat is more open and allows the inclusion of other living mounts such as Rhinoceros, Elephants, Dragons etc.
 
So I would say keep Mounted Combat and remove Combat on Horseback since Mounted Combat would essentially include and cover fighting in battle while mounted on a horse as well as other creatures both great and small.
 
I suppose you could say, strike one!

Agreed - keep Mounted Combat, remove Combat on Horseback - strike two!