If, after an action, units and Leaders controlled by different players are in the same region, they may remain as separate Armies or a mixed Army can result.

If the Armies remain separate, each player keeps the control of his own units and Leaders. If the total number of units of the two Armies exceeds the stacking limit, the players must remove one unit each, starting with the non-Leading player, until the limit is respected.

The troops of the two players may become a mixed Army if both players agree to this; they must become a mixed Army if the region is attacked.

The controlling player of a mixed Army is the player who controls the highest number of Army units in the region. In the case of a tie, the player with the highest number of Elite units is the controlling player. If there is still a tie, the current Leading Player is the controlling player.

Only the controlling player may use actions to move or attack with the mixed Army, and play Combat cards for that Army.

If the number of units changes, the control of the mixed Army may be transferred to the other player. Note, however, that the controlling player may not deliberately split an Army (during either movement or attack) so that he loses the control of the acting Army.

A player may regain control of his units in a mixed Army by simply using an action to move these units out of the region with the mixed Army.

A mixed Army is still subject to the political restrictions (such as not being able to move across another border) of any non-belligerent Nation that is part of a mixed Army.