Forward Deployment After both players have deployed their armies, including Infiltrating Detachments, but before the first round of the battle, if all models in a Detachment have the Forward Deployment special rule, the Detachment may make a special move.
The controlling player can move each Forward Deployment Detachment on the battlefield up to a number of inches equal to its Movement characteristic, ignoring Difficult terrain and Dangerous terrain rules. This move can the Detachment outside of its deployment zone and a Detachment can Garrison a Structure if they are able to.
If both players have Forward Deployment Detachments, then the winner of a roll-off chooses who moves their Detachments first.