Just a thought, but why did you do the attacks as an immediate attack and a journey time back home?
You could have a 4 hr journey to the attack, and a 4hr journey back, and have other kingdoms that could defend. say the 1st hour, you can raise defense from others in alliance etc, but an hour into the journey if you haven't gotten defense your on your own, or with the defenders you can find in the first hour.
The attacker could also use the spy to check on the attack, if they got defense, recall the attack if necessary.
just an idea, it would bring more team play