(Many thanks to Delta93 for proofreading!)
In retaliation for the attack on Canterlot, Princess Celestia leads a crusade against the Changeling Horde. The Elements of Harmony fight bravely in the campaign, and are rewarded with landed titles in the newly-conquered Duchy of the Outer Lands.
Friendship is magic, but will it prevail against the cold, hard reasons of state?
Tagged as 'Alternate Universe' because of divergence following Season 2's ending. But if possible, I will try not to go too far off track. The story will probably have a more medieval atmosphere than canon.
Rated 'Teen' just in case.
While the story will contain all of the Main Six, interactions between Applejack, Rainbow Dash and Twilight will (if according to plan) drive most of the plot. Thus the tags.
Other characters from MLP:FiM might be mentioned in the story, and they will deviate (a lot) from 'acceptable' canon. List so far: Princess Celestia, Spike, Applebloom, Big Mac, Granny Smith, Angel, Twilight's parents, Cadence, Shining Armor, Rainbow Dash's parents, Discord, Luna, Lightning Dust, Pinkie Pie's parents, Octavia, Pinkie Pie's sister (Inky), Sweetie Belle, Scootaloo.
Inspiration from the strategy game "Crusader Kings II", the novel, "Romance of the Three Kingdoms", and a metric ton of Chinese historical dramas.