For almost a thousand years, humans have journeyed into the farreaches of space, colonizing thousands of worlds and forming star-spanning allainces. From these grew the five vast star empires that make up the Inner Sphere.

But the Inner Sphere is divided. Its ruling dynasty warred constantly over colony worlds with valuable resources. These titanic struggles led to the development of BattleMechs: gigantic, humanoid battle machines bristling with lethal weapons weapons. From the twenty-fifth century onward, these walking tanks ruled the battlefields. BattleMechs and their skilled pilots changed combat forever.

As the price of conflict grew, the Inner Sphere tired of war. In 2571, the five ruling Houses joined together in the Star League, a federation led by a first lord and served by its own army. For nearly 200 years, the Star League brought the Inner Sphere peace and prosperity.

In 2751, the sudden death of its First Lord left the Star League in the care of a child. Young Richard Cameron ruled in name, but the real power lay with the 5 Council Lords. Ambitious and distrustful, they plotted against each other, while an evil genious named Stefan Amaris wormed his way into Richard's trusting heart. In 2766, Amaris assassinated Richard, and all known Camerons, and took control of the Star League in a bloody coup d'etat.

The Star League Defense Force (SLDF), commanded by the brilliant General Aleksandr Kerensky, refused to accept Amaris' rule. For 13 years, they fought him in a bitter civil war that was the largest conflict ever fought by humanity, before or since. Kerensky's forces won, but at a terrible price. In the chaos that followed, the Council Lords were all determined to step in as First Lord. Despite the efforts of Kerensky to hold it together, the Star League dissolved in 2781.

Unable to halt the impending conflict, Kerensky appealed to his soldiers to join him in leaving the Inner Sphere. Nearly 80 percent of the SLDF heeded Kerensky's call to build a new Star League somewhere far beyond the explored universe. In 2784, Kerensky and his followers abandoned their homes and headed into uncharted, presumably never to return.

War followed war in the wake of Kerensky's dramatic departure. For nearly three centuries, the Houses of the Inner Sphere fought in vain for the right to rule the universe. These Succession Wars brought new alliances and cost the Inner Sphere precious, irreplaceable technology. Constantly maneuvering for position, the House Lords assumed that the greatest threat they would ever face was each other.