After the Changeling Lands, under Queen Chrysalis, invaded Olenia, Equestria rallied to defend its neighbor. The war lasted three years, and saw ups and downs, loss, victory and defeat for both sides. However, in the end, the two allies overcame the changeling hordes. Chrysalis fled, and a treaty was signed by a lesser queen willing to take her place.
The trouble is, many changelings still consider themselves to be Chrysalis' subjects... and refuse to allow their nation to be occupied, or changed, without a fight...
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Gore is for occasional mention of, or scenes with, major wounds and means of death, though its not constant or focused on throughout the story. Violence is for the combat scenes. Dark is for, well, it's soldiers fighting guerrilla changelings, and those changelings largely support an evil ideology.
Written for Equestria at War, including the 2019 writeoff. The reason I am not part of that group is because HOI4 currently isn't working for me, mods or no, and as such I cannot even play EAW or experience what it is like except from watching other people on Youtube.
Note that I don't endorse hate. I'm not for war crimes or for the evil feelings caused by combat. However, both these things happen, especially in an insurgency where most of the population supports the insurrection and regularly espouse hate, disgust, or contempt toward the occupying forces. I don't endorse or promote it, but it does, sadly, exist.