1. The Lannisters Are Still The Greatest Military Force In Westeros
One aspect that wasn't sufficiently investigated in the show is the quality of leadership demonstrated by Robb Stark. Throughout the first two seasons, Robb Stark outsmarted the Lannister forces, emerging victorious in each battle. This, along with the violent Battle of the Blackwater, led to the deaths or abandonment of many Lannister soldiers. The Lannisters may seem to be in a pretty good position right now. The War of the Five Kings caused them a lot of troop losses, but the house has managed to survive by using sneaky plans, unstable alliances, and the unacknowledged intelligence of a particular dwarf. The Lannister family is heavily dependent on their partnership with the Tyrells. That's why Tywin is working hard to maintain the alliance, even though the two families don't like each other. Due to the fact that the Tyrell army has stayed away from all battles except for defeating Stannis' troops at Blackwater, they now control one of the biggest combined forces in Westeros.