User blog comment:Zippertrain85/"Why the Empire Should Prevail Over the Stormcloaks! Part 3 (Economics)" Refuted/@comment-24355185-20131229221102/@comment-9062114-20131229221221

I should've mentioned that. In addition as Harold pointed out, one of their port cities is Windhelm. Which was under Stormcloak control since the beginning of the game.