Manga, LN or Anime similar to Arslan Senki and Kingdom which have historical settings, war, betrayal, loyalty, adventures, friendship and romance.

I'm not sure if you're okay with shoujo but Kanata Kara has every single one of those elements.

It would be helpful if you had public lists! So apologies ahead of time if you've read these before:

Chang Ge Xing
Historie
Mujang
Seirei no Moribito
Shin Angyo Onshi
Shoukoku no Altair
Shut Hell
The Ravages of Time (though I am honestly really behind on this, so I'm not sure of its current quality)
Vinland Saga

And, do you have a preference for time periods? For instance, Gunka no Baltzar is a pretty good historical manga set in an alternate universe Germany during the industrial revolution, and Golden Kamuy is a great action (and cooking) manga set right after the Russo-Japanese War (so pre-WWII).

There's also some interesting westerns, ergo Peace Maker, Justice, etc. Though I'm not sure if that's what you want when you mention "historical".

Twelfth Night
Basara this seems obvious but I'll say it anyway