Time
"The immediate goal of the Sekigahara Confederate upon any such invasion would be to ensure that no conflict occurs within their territory." Commission Feristen explained. "After all, ideally our goal would be to ensure the conflict occurs within their border, this would inflict the most amount of damage to their base and would ensure that their expansion is hindered the most. Their goal is the exact opposite. They'll want to minimize the amount of damage we inflict, while also maximizing our losses."
Rui nodded. This was common sense. It was impossible to prevent any damage from being inflicted in such a conflict, but at the very least the damage could be significantly minimized depending on their strategy and tactics.