>>1543414Romance of Three Kingdoms obviously. Read the Sangokushi manga if you don't want to read the novel or watch the tv series.
Legend of Galactic Heroes. Aka 3 kingdoms in space.
If you're not allergic to Chinese stuff, then Reverend Insanity. It's a Chinese webnovel, heavily inspired by 3 kingdoms.
For Korean stuff, Absolute Regression is the gold standard. I don't think I will ever read anything better in my life. There are manhwa and novel. Both excellent.