"It was necessary for Luna and Celestia to become soldiers, as well as rulers, in order reunite Equestria and restore peace across the lands, following the chaos of Discord's reign.



But they did not do so alone. From the best and most virtuous of their army, they chose ponies to become sentinels, paladins, and healers to roam the land alone or in teams, restoring harmony and protecting others wherever trouble lurked."



~Preface From "The Early to Middle Reconstruction Period," Chapter 14