User blog comment:Zippertrain85/"Why the Empire Should Prevail Over the Stormcloaks! (Part2)" Refuted/@comment-1600847-20131216222200/@comment-9062114-20131221023519

The 4th Legion is just one Legion, assigned to this whole Skyrim becoming independent incident. Odds are most Imperials and Bretons don't want to work on that, in addition the 4th Legion is already the largest Legion, so they may want new recruits from outside Skyrim to assist those.