@way2slo:
My question would be:Â Why would you want to?
The only reason I can think of is to move an AC to pick up planes from combat. Other than that, wouldn’t you want to just include those units in the combat itself?  :?
Not necessarily.
Let us say that you undertook a battle in which you thought that you would either withdraw from or win with only a slight edge. (You may choose to attack, but withdraw early, to weaken an enemy stack of forces. After you withdraw, your forces are vulnerable to enemy attack, but if you move up reinforcements, you strengthen your position. In theory, then, you can attack, inflict casualties, and retreat to a strong place that you cannot be attacked at).
But anyways, say you thought you weren’t gonna do so hot, but suddenly you kick ass all over the place, and lose nobody.
So then, instead of having 1 infantry to hold that territory, you suddenly have 6 infantry. Plus your opponent just got whuppped.
So you move up reinforcements that you WERE going to hold back - those reinforcements help you secure the territory, because the enemy’s so weak that the enemy can’t really risk attacking your pile of units.