A House is said to control a land area when it has at least one Footman, Knight, or Siege Engine in the area, or has previously established control in that area by placing a Power token there.
Establishing Control Of An Area
If a player vacates a land area with all of his units, he stands to lose any benefit gained from controlling that area unless he chooses to establish control.
When a House vacates a land area (i.e., all its units leave during a March Order) the House may elect to establish control by placing a Power token from its available power in the vacated area (a House can never establish control over a sea area). Once placed on the game board, this Power token represents the support of local nobles as well as investments in guards, tax collectors, and bureaucrats loyal to the controlling House.
If friendly units enter the area again, the Power token remains there, unaffected (and continues to establish control if the area is vacated once more).
If a player leaves an area vacant before initiating a combat, he must decide whether or not to establish control of the vacated area before the combat begins.
A Power token on the game board is returned to the Power Pool only after an opponent takes control of its area. Marching into an area containing only an opponent's Power token (i.e., no enemy units are present) does not result in combat, and the Power token is simply discarded to the Power Pool.
Power tokens do not aid the defender in combat, nor do they count as "Power icons" printed on the game board (for the purposes of Consolidate Power tokens or the "Game of Thrones" Westeros card).
Only one Power token can be in an area at any one time. If a player has no available power, he's unable to establish control.
Important: A player may only establish control when vacating an area with a March Order. Events that would leave an area vacant (such as negative effects from a Wildling victory) does not permit a player to establish control after the last unit is destroyed.
Controlling Home Areas
Each House has a home area marked by its House shield (printed directly on the game board). From the beginning of the game, a House is considered to have established control of its own home area, meaning the printed House shield functions like a Power token that cannot be removed.
Players can control enemy home areas by either a) keeping friendly units in these areas, or b) by establishing control over the enemy home area. When establishing control over an enemy home area, the friendly Power token is placed directly over the printed enemy House shield.
If a player chooses not to, or cannot, leave a Power token behind when vacating an enemy player's home area, control of that home area immediately reverts back to its original House.
Reminder: A retreating army can never retreat into an area containing an enemy Power token.