Ranger "Refugees" - [5th campaign, 1st mission]

Damn, I also struggled and couldn't defeat the demons until I removed the reinforcement from several posts, or rather, replaced it. You can't actually remove it, and then I defeated him without any problems. Attacking posts is a minor issue; it's not even worth worrying about, even if they capture them, you can quickly take them back.

This depends on the difficulty level and the game version. In version 1.5, it's not easy to remove the reinforcement from posts on a hero. Yesterday, I defended a post and lost about 90% of my army. I clicked "end turn." They captured the next post, and the mission failed.

Apparently, after defending a post, a full turn must pass before the enemy captures the next post. I defended a post, but they captured another post in the same turn. I had nothing left to defend with. If the mission hadn't failed, I would have run back to the castle, hoping that there would be no more attacks on the posts. It was the 4th week.