This series is interesting because of a kind of "micro-management": Every Viking, it doesn't matter if farmer or soldier, has its own needs.
Every person has to be provided with food or has to sleep. A worker lays down tools, when he is tired and goes to sleep until he rested.
Furthermore there are differences between sexes, a "supply" of Vikings can only be guaranteed when you let marry couples and when you tell them to produce kids.
This "micro-management" and the consequential learning curve makes this game so special for people all over the world.