We got another developer diary from the new Paradox game Millennia!
This time the diary is about the combat in the game. The combat is different to civ games, as you can group multiple units into armies (a bit similar to Civ3), but multiple armies will fight each other in a simulated battle, on which you have no influence on itself, besides the troop composition. There are more details in this dev diary, like the production of the units and how leaders are used on the battle field.
For all this information please check this thread.