The army had already geared up to retake Madina city, so we've got a massive army ready to swoop in and take their capital (since it's only a quick boat ride away...).
Forgive me if I'm skeptical of this.
Madina couldn't put together a massive army and launch an invasion with it if they were handed 15,000 CS on a platter. As it is, you are attempting to launch an invasion across what I assume to be a 12+ hour journey, and your entire realm has only 6,000 CS. I assume Candiels has some kind of walls.
You may win, but I have a hard time believing Madina possesses any massive army, or that it will defeat Auvrandil so easily. My main memories of Madina consist of them failing to garrison Paisly, attempts to use infiltrators to eliminate armies, and three successive whole-realm invasion attempts against Paisly in a row defeated by Terran's special tasks army.