It was the middle of the twenty-eighth century. Two hundred years after the Age of War, all of mankind now lived, united, under one flag: the Star League. Defending and policing this vast realm nearly 3,000 worlds strong was the largest army ever known to humanity: the Star League Defense Force. Harnessing the largest fleet of WarShips ever assembled, the most advanced technologies in BattleMech and aerospace design, and the finest, most disciplined training regimens in known space, the SLDF was the invincible might that kept the feuding Houses of the Inner Sphere in line. Field Manual: SLDF describes the single greatest military force the Inner Sphere has ever seen: the Star League Defense Force. Including a brief history and overview of the SLDF, its formation, organization, and training programs, this book provides the most detailed look ever at the army that protected the Inner Sphere before the treachery of Stefan Amaris and the Succession Wars that soon followed. Special rules are also included, enabling players to create Star League forces for use in campaigns set in one of BattleTech's most storied eras.