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Three way civil war, Princess Celestia with Twilight and Rarity. Princess Luna with Fluttershy and Pinkie PIe, and Cheerilee with Applejack and Rainbow Dash. 

Who would win? My bet is on Princess Celestia just because of unicorn Twilight, but Luna has the higher combat potential of the princesses. Cheerilee would be some random usurper without magic or much support, so I don't know why Rainbow Dash or Applejack would side with her.