In the Frequently Used Terms on page 15 of the Rulebook you can read :
Controlled Area
: A player controls an area if he has at least one plastic unit (including routed units) of his color and/or one of his strongholds in the area.
Having only a hero or neutral units in an area does not make an area controlled. Players always control areas in their home realm unless enemy units are present.
The current definition of Controlled Area implies that you control an area if you have a friendly unit in it, meaning, when you attack an opponent, the area which you attack becomes " controlled" by both players because you both have at least one unit in it.
This seems highly illogical and unintuitive to me as I would rather think the area becomes "uncontrolled" as soon as two armies occupy it.
What's more, when you start a battle that area is at the same time a
1- controlled area ( you have a unit in it )
2- enemy area ( enemy has a unit in it - thus controls it )
3- friendly area ( you have a unit in it - thus you control it )
4- contested area ( there's a battle or duel going on here )
IMO only 4 should apply to a battle area and none of 1, 2 or 3.
So, I think the definition of Controlled Area is currently incomplete and should read like this :
A player controls an area if he has at least one plastic unit (including routed units) of his color and/or one of his strongholds in the area and there are no enemy units or uncontrolled neutral units in that area.
The fact that there is something wrong with the current official rule is also illustrated by the last sentence : "Players always control areas in their home realm unless enemy units are present."
So, ... you always control the areas in your home realm
but ... if there are enemy units present in them, you no longer control that area, ... even if you have units in that area.
And yet ... the rule says ( about area control in general ) that you control an area when you have at least one unit in it.
Complete contradiction.
IMO, what the designer meant is
Friendly Area : you have at least one friendly unit and / or Stronghold in the area and there are no enemy units in the area.
Contested Area : you and an opposing player ( both ) have at least one friendly unit and / or Stronghold in the area.
Enemy Area : an opponent has at least one unit and / or Stronghold in the area and there are no other player's units in the area.
Controlled Area = Friendly Area