What if frieren got a cloning spell...
I dont remember this from the manga.
This makes me realize there's way too little WW2 armies vs monsters anime
not the best but fits the bill (army vs monsters) https://myanimelist.net/anime/52461/Rougo_ni_Sonaete_Isekai_de_8-manmai_no_Kinka_wo_Tamemasu
ah yeah, that one was kinda fun
The closest I can think of is gate. Modern military in a fantasy setting
true, this one probably fits the requirements best. it was alright. I'm really surprised this isn't a bigger genre. Something like The Saga of Tanya the Evil but with Monsters would be cool.