Just wanted to clarify one rule quick: When an army is forced to flee from a losing battle, all of its units are routed as well. If an opponent then moves a single unit into the area they retreated to, the routed units don't even join the battle, and thus they automatically lose the fight 1-0 and are all destroyed?
You're correct IMO that a single standing unit can destroy an entire routed army by moving into the routed army's area, forcing them to retreat and thus be destroyed.
I understand the logic behind it, but it makes it incredibly difficult (if not impossible) to attack somebody's stronghold with the goal of weakening it for a second attack to take it, since your army can be attacked by a single archer and wiped out completely.
Since you can activate a certain area only once a year, I think you will not be able to "attack somebody's stronghold with the goal of weakening it for a second attack to take it"
Sure you can attack it again, but that will be the "next year" and by then your army is "standing"again.
The only way to attack the same area twice IN THE SAME YEAR would be if there were a way to remove the activation token you put in that area ( like with the Warfare Strategy Card in TI3 )
... or you could of course ... attack in Winter and then attack the same area again in the spring of the following year ... that gives you two consecutive attacks.