Let us not break the combo:
Bernard Cornwell. Why? The ol' man like a bit o' war, I guess, so he describes them with lots of details and ****. The only thing I don't like is that in... well, most of his series, the story sounds like a bad MMORPG: "And the protagonist X goes to town Y with the army, but there villain Z kills X's best friend, B, so X swears revenge on Z" and that is followed by pretty much running from village to village, town to town. Sure I like it how he adds detail to it, but deep down all the stories have the same structure. Still, reading the battle of Crecy was awesome.
And that's pretty much my only "favorite" author. I could have said Tolkien, but that's absolutely... cliche. It's just like someone saying "oooh, I like Shakespeare, Allan Poe...". Actually, nevermind me.