SPOILERS!!!!
Pretty much everyone not in the Starling party gets killed in the war. Remember Argeria or w/e his name of Blue Moon party? Cut in FUCKING HALF by an enemy swordsman who's the #2 of the entire war under the big bad. Jode Exarion? Murdered and betrayed by the Big Bad in a battle that was rigged against him from the beginning because of planning/setup for that moment. Other students? Dead. IDK if Donape survived or not, I can't remember. Teachers/professors? Most dead.
It just becomes a bloodbath, which while realistic, is really off-putting and just morbid.
no links allowed here TMK, but if you go to the subreddit about this series, they have the entire series with links.
The amount of violence and death was considered excessive and unnecessary by a lot of readers, but the fight with big bad is pretty good, and vastly superior to those appearing in typical shonen manga (especially Naruto and Bleach, ugh).
Not in the Starling/Sparrow party = dead pretty much.
I believe minor members/allies like the incredibly large fire-using first year and Donape and the pleb professor all survive, but more prominent ones like Joad Exarion are all slain; like I said, some of it becomes preeeeeeeeeeeeeeeeeeeeetty bloody.
Hence why I hope the manwha takes a bit of a different path, if not entirely different. Shit went too close to Naruto/Harry Potter territory with the "start hopeful but end on a very bittersweet note."
The rest of this series gets pretty fucking gruesome, bloody, and sad now. I really, really hope some of that is removed or edited. The novels were just so fucking sad.