Do your army units "level up"?

[botski]

I couldnt find any mention of this in the manual and couldnt find any indication of such when I clicked on a unit (I would have expected a bar to indicate bumber of points needed for the next level). I am a level 6 mage and dont seem strong at all. I keep buying new units but this is hampering my ability to raise a significant amount of gold needed for a quest. If the units do indeed level up, perhaps I should have spent more effort keeping them alive.

Thanks for any tips!