Nejimaki Seirei Senki: Tenkyou no Alderamin, Vinland Saga Recommendations
cruelty of war,awesome tactics on how to get a upper hand in war,ways to win your enemy's trust - all are pretty nicely presented in the two animez. to be honest,these two are literally gems in the war genre.
[P.S. if you liked the character solark of alderamin, then you'll be fascinated by the characterization of askeladd - that i can ensure you]