*** spoilers ***
Port Hope refers to the land of Tarth, i.e., the folks who gave you Archers and asked you to fight Trolls. Yeah it is confusing that they call it that.
When you sail back, and you may actually have to land a unit off your boat to go talk to them, they'll give you a few more archers and another boat. If you also go talk to the miners they'll give you a little something too, i think it was some supplies.
Sorry if I confused you in my previous post when I said "marked objective" -- yeah I meant the boss battle. It should have been revealed and (very subtly) highlighted on the cloth map that you see when you zoom out far enough, and indicated the place where your "land" and "sea" armies are meant to converge. Sounds like you found it.
Dragon and his friends have some nasty AOE spells that seem to ignore armor, so you need veterans and/or squads to survive long enough to take him down. In my playthrough i tried to get my troops some extra veterancy by training on the Umberwolves and other monsters in the desert, but they took a lot of damage and i couldn't heal so far from town. So I brought "fresh" troops trained as squadrons with one chevron of veterancy; you can choose those as an option on the training tab in your town once the appropriate Warfare techs are revealed.
