Ian Cameron, ruler of the Terran Hegemony, concludes decades of tireless effort with the creation of the Star League, a political and military alliance between all Great Houses and the Hegemony. Star League armed forces immediately launch the Reunification War, forcing the Periphery realms to join. For the next two centuries, humanity experiences a golden age across the thousand light-years of human-occupied space known as the Inner Sphere. It also sees the creation of the most powerful military in human history.

Every last member of First Lord Richard Cameron’s family is killed during a coup launched by Stefan Amaris. Following the thirteen-year war to unseat him, the rulers of each of the five Great Houses disband the Star League. General Aleksandr Kerensky departs with eighty percent of the Star League Defense Force beyond known space and the Inner Sphere collapses into centuries of warfare known as the Succession Wars that will eventually result in a massive loss of technology across most worlds.

A mysterious invading force strikes the coreward region of the Inner Sphere. The invaders, called the Clans, are descendants of Kerensky’s SLDF troops, forged into a society dedicated to becoming the greatest fighting force in history. With vastly superior technology and warriors, the Clans conquer world after world. Eventually this outside threat will forge a new Star League, something hundreds of years of warfare failed to accomplish. In addition, the Clans will act as a catalyst for a technological renaissance.

The Clan threat is eventually lessened with the complete destruction of a Clan. With that massive external threat apparently neutralized, internal conflicts explode around the Inner Sphere. House Liao conquers its former Commonality, the St. Ives Compact; a rebellion of military units belonging to House Kurita sparks a war with their powerful border enemy, Clan Ghost Bear; the fabulously powerful Federated Commonwealth of House Steiner and House Davion collapses into five long years of bitter civil war.

Following the Federated Commonwealth Civil War, the leaders of the Great Houses meet and disband the new Star League, declaring it a sham. The pseudo-religious Word of Blake—a splinter group of ComStar, the protectors and controllers of interstellar communication—launch the Jihad: an interstellar war that will ultimately pit every faction against each other and even against themselves, as weapons of mass destruction are used for the first time in centuries while new and frightening technologies are likewise unleashed.

Under the guidance of Devlin Stone, the Republic of the Sphere is born at the heart of the Inner Sphere following the Jihad. One of the more extensive periods of peace begins to break out as the 32nd century dawns. The factions, to one degree or another, embrace disarmament and the massive armies of the Succession Wars begin to fade. However, in 3132 eighty percent of interstellar communications collapses, throwing the universe into chaos. Wars almost immediately erupt and the factions begin rebuilding their armies.