Before we get to the story, a few things need saying. First off, I do not own the Pevensies, Narnia or anything therein. That'd be the property of whomever actually owns them. Secondly, thank you to rthstewart, whose writing inspired this. Go check her stuff out, it's brilliant in so many ways.
Peter may have been the High King, but he was not in charge of the intricate inner workings required to keep a kingdom going. That dubious honor fell to the combined wits of the two smartest Beings he knew, Susan and Edmund. Between the two of them, they knew almost everything of importance in Cair Paravel, and in the greater world as well. The Pevensies had their diverse roles in keeping Narnia functioning, each doing what suited their skills the best. Lucy was the shining light, Peter the defender, but Edmund and Susan were the ones who found the Calormene spies, who planted counter-intelligence, who set up the communication network that extended through Narnia and beyond.
Lucy may have known every inhabitant of the Cair, but Susan knew who had lost family in the Winter War, and fighting for which side. She knew when politicians were trying to take advantage of her gender, and how to gently use that to Narnia's advantage. She could politely turn around any argument against the politician who tried to undermine her and her siblings.
Edmund trained with his brother on the battlefield, yes, but he also trained in the courtroom. It was his lot to be judge and jury, to figure out who could be redeemed, and who could not, to forgive everyone for their crimes, whether or not they deserved it. While Peter led the charge on the battlefield, it fell to Edmund to lead in governance, writing the laws and treaties that kept Narnia safe.
Their jobs went unsung quite frequently, but they had to be done. Many of their subjects did not even know how much went on outside of common knowledge to keep them safe, how much was sacrificed to ensure that they could go about their lives in peace.
As always thanks for reading, and please review!