Ok, two Stark players are playing against each other.
Player ONE wins a military on offense. Player TWO plays Feigned Retreat.
Response: If an opponent would win a Military challenge against you, kneel 2 influence to cancel the determination of challenge winner. You automatically win the challenge.
If player ONE also has a Feigned Retreat in hand, could he then play it? Or has the "determination of challenge winner" window already closed, and thus there is no opportunity for responses?