When I declare him as an attacker in the military challenge and win, I choose and kill a character controlled by the losing opponent but do I do this before or after the opponent chooses and kills his character (as a result of losing a challenge). Also if I do it before, does the opponent still have to kill his character as a result of losing the challenge?

ed00011 said:

Look at flowcharts in FAQ:

1. Determine winner of challenge
2. Challenge result is implemented
3. Reward for unopposed challenge is awarded
4. Renown is awarded

5. Passives (e.g. deadly, Fury of the Wolf)

6. Responses (e.g. Robb)

Claim effect/challenge result always happens before any Response (that doesn't use the word "save" or "cancel").

Now what if I'm defending and I choose Robb Stark as a defender. Attacker has a character with deadly. I win and so i can kill opponent's character but that can happen after the deadly thing is resolved. So do I have to say that I activate his response before (and remember to execute it after Robb is in dead pile) or in this particular situation there is no way to execute Robb's response (because he is dead - target of deadly)?

Rob becomes moribund (see FAQ page 16) if you kill him - he stays on the table and is allowed to interact with the game as normal until it is finally (and physically) placed in the dead pile after all players play all their responses.