Tensei Shitara Slime Datta Ken (WN)

There were many wars. Which one are you refering to? Spoiler Alert there was the war with the orcs, later with falmuth, clayman, the western church, the eastern empire, the giants, the angels and lastly the final battle where we had most of the still alive demon lords against Yuuki to dectate the fate of the world.

Where do you even read LN?

All chapters after the battle with yuuki are like side stories from Fuse. They are worth reading i guarantee it.

Web Novel ≠ LightNovel ... WebNovel = Draft/First version. Before being recognized by a publisher. A "bookcase" used by oriental authors, often without being "active professionals", to build a fan base or raise extra money while using their skills to entertain a significant number of people. ... LightNovel = Official version sponsored by a publisher. If coming from a WN, the author is encouraged to extend his story and better develop the narrative, in addition to having the authority (slightly recommended) to alter parts of the plot of the story, without harming the original basis. It is the version used as a basis for possible adaptations in other media (anime, manga, etc).

i was today years old when i found out this is the meaning of WN and LN. Thanks

This is WN the anime and manga follows the LN LN is like a improve version of the WN where they fix some plot holes and stuff so it's not surprising that this differ from the Anime

where do I read that

it is a book!