Adventurers plops, ripe for the grabbing

As the Emperor of Mightyland, your job is to defend the border against the bloodthirsty hordes of Badguysia. To do this, you must build up a wall and other defenses on thousands of miles of border. Similar mechanics to a tower defense game, but scaled up to tremendous proportions that force a few RTS elements into it, & also you take breaks from overworld mode from time to time to wander your palace and interact with your underlings, some of whom are secret agents of the enemy.