It's in the prequels I'll link them to you if you want to watch more LOTGH once you're done in the main series 
Warning though, there's no politics, or as little as there can be. At least as far as I know from what I've watched of "series 1" (which is Reinhard's side of the story.) So you'll get all the crap you got from the early series of LOTGH, and by that I mean the blatant incompetence of commanders. But there are more compelling characters amongst the Imperial Ranks who aren't Reinhard's future Officers.
And yes, they certainly are his flaws. In the prequel, Kiricheis mentioned another. I can't recall the early series well, but it's almost certainly his conviction. What Reinhard would do within the blink of an eye, even if he didn't want to, Kiricheis couldn't.
Or at least this is what Kiricheis said (and proved in the Dishonour arc of Gaiden.)
P.S
There are two cameos of Yang in series one which just made me grin like an idiot.
One where Reinhard mentions "will I ever had a worthy rival" (or something like that) and another where Schenkopp says "will I ever have a competent commander before I die?" In both he says nothing, and it's just for a second or two, but god is it glorious to just see him xD
Can't wait to get to series 2 which will be all about Yang.
The prequels not delving into politics is just fine. I don't view entertainment solely based on that aspect. If something has political factors and they are actually handled in a capable manner, then it certainly enhances my viewing experience, but it is not an obligation for me to enjoy something. Though more incompetent characters sounds disheartening...
Haha, do like how so many individuals are just magically drawn to Yang Wenli. He certainly has an aura that makes one simply admire the guy, and it is all warranted.
I mean, I don't mind. Certainly, LOTGH is not the show for everybody.
Last time when I pointed this out, you said that such people are ignorant and should not be payed any heed to.
*angry stare*