Re: Gregor & Tarly trapping the northmen, I’m getting maybe Tarly isn’t quite a military genius, but that seems like obvious tactics. Which do you think is more likely the cause? Gregor charging into the retreat path Tarly would have left out of bloodlust (or Tywin’s vindictive orders), or Tarly being affected by Robert’s successful retreat, maybe taking the lesson that you can’t count on an ally to finish a defeated foe, and not want Glover & Tallheart to rally elsewhere? Or some other factor?

Well, it’s not such obvious tactics, because outside of some of the best premodern armies ever (the Byzantines, the Mongols), people usually went for the complete encirclement. But there are other things that could have happened:

• Gregor charging in recklessly is quite in character – his wing of the battle takes the heaviest casualties in the Battle of the Green Fork, he loses half his men at the Battle of the Fords, etc. 
• It could be that Robett Glover is good enough of a commander that he reacted well enough to a bad situation to make the Lannisters pay dearly for their victory.
• Or something else.