Seeing as you can only claim an area in the end of the activation phase, and your reinforcements only come on in the end phase.
CONTROLLING A SECTOR wrote:
DURING THE PLANNING PHASE, the player with the most ships in a sector controls that sector.
REINFORCEMENT SHIPS wrote:
Reinforcement ships that are brought into play are set up during the Planning Phase.
Neither one says anything about either the Activation Phase or End Phase.