By the 31st century, humanity has spread to thousands of worlds, while a handful of powerful empires wage continual war for the right to rule the stars. Foremost among the weapons used in that struggle are BattleMechs. Loaded with autocannons, missile launchers, lasers, and charged-particle beam weapons, these fusion-powered war machines of articulated armor stand upward of ten meters high. Piloting them are MechWarriors, the best, most intensively trained men and women available. Like the armored knights of an earlier age, MechWarriors are popular heroes, and their exploits are the stuff of legends.

Breakthrough (2001-2100):

At the beginning of the 21st century, life on Terra had not changed much from what it had been at the close of the 20th century. Despite attempts at reconciliation in the 1990s, the planet's two giant superpowers still opposed one another, but now their tangled web of weaponry stretched outward into space. Over the next 100 years, however, the situation changed dramatically. By the end of the 21st century, the people of Terra stood poised in apparent unity on the brink of their first expansion into the stars.

Politically, humanity's new age began in 2011 when the bloody Second Soviet Civil War tore that nation permanantly asunder. As the Soviet strife threatened to bring the rest of the planet to the brink of nuclear war, a joint force of North American and Western European troops intervened to end hostilities in 2014. This outcome greatly strengthened political ties between nations of the Western Alliance, resulting in a formal unification of Western military forces. By 2024, the Western Alliance included Japan, the newly liberated Eastern European nations, and the now-separate seven Russian states. Replacing the defunct United Nations as a world forum was the Alliance Parliament. As a vigorous sponsor of scientific research and space-exploration activities, the Alliance handsomely rewarded similar efforts by its member states.

As the economic benefits of Alliance membership became obvious, nation after nation petitioned the Alliance for membership status. By 2086, the Western Alliance had become the Terran Alliance, embracing more than 120 member-states. A complex formula based on date of entry, wealth, population, and military power determined each member's voting strength in Parliament.

The 21st century was an age of unsurpassed scientific innovation, most notably the development of fusion power as a major source of power. Alliance scientists built the first full-scale fusion reactor in 2020, and sent the first fusion-powered spacecraft from Terra to Mars in 2027. The voyage took only 14 days, a fraction of the five months the trip had previously required. Because of the fusion-power plant's efficiency, space vessels could now maintain higher-acceleration burns for much longer periods.

The development of efficient fusion drives made possible the first widespread exploration of Terra's star system. By 2050, the Alliance had scientific outposts throughout the Sol system, had dispatched unmanned interstellar probes to Tau Ceti, Epsilon Eridani, and Epsilon Indi. By this time, private multinational corporations also began to participate in spacefaring activity, establishing mining colonies in the asteroid belt, and then transporting entire asteroids from the belt to the Terra-Moon system. These corporations also engaged in technological research that resulted in breakthroughs such as the development of dense-but-lightweight materials for spacecraft and space-station construction and a variety of small, portable fusion reactors for equipment use.

Not all the breakthrough research of the 21st century took immediate effect, however. Working together at Stanford University, America's Thomas Kearny and Japan's Takayoshi Fuchida published a series of papers from 2018-2021 that attacked the theoretical underpinnings of modern physics. The scientific community ridiculed their work, and both men died in obscurity before the century was half over. As had been the case with so many innovators, only future generations would respect and honor the value of these two men's daring research. It would be another 80 years before their theories would come to fruition.

Meanwhile, medical prosthetics research had led to the development of polyacetene fibers called "myomers." Under the influence of electricity, bundles of these fibers would contract strongly, like muscles. Unfortunately, the minimum bundle length required for the process was far longer than any human limb. This line of research would lie fallow for the next three centuries.

Exodus (2102-2313):

In 2102, scientists announced the greatest scientific breakthrough of the last two centuries, the theoretical prototype for a faster-than-light starship. Ironically, their work was based on the once-scorned theories of Kearny and Fuchida. The Terran Parliament authorized the Deimos Project, a crash program to develop an FTL drive. Although the Deimos project culminated in the maiden voyage of the first FTL ship to Tau Ceti in 2108, the billions spent on it created resentment and even rioting in some of the poorer Alliance member-states. This rift in the apparent unity of Terra was never completely repaired and the struggle between the "haves" and "have-nots" would continue to plague the Alliance. Shortly afterward, Alliance shipyards began producing FTL-drive ships. By 2116, the first permanant space colony was established on Tau Ceti IV (New Earth).

As engineering improvements reduced the cost of building FTL ships, corporations and even dissident private groups began to acquire their own vessels to exploit the seemingly limitless potential of the stars. The Terran Parliament soon acted to place colonization under its sole authority, passing laws requiring that all ships have a Terran naval escort, and placing all colonies under Terran jurisdiction in the form of an Alliance-appointed governor. In 2172, the first Alliance Grand Survey reported the existence of more than 100 settled human colonies spread across a sphere 80 light years in diameter. The fourth survey, conducted in 2235, recorded the settlement of more than 600 worlds.

As more and more planets were settled, the colonists began to encounter the problem of impure water supplies suitable neither for human consumption nor for irrigation. As the costs of water purification equipment were prohibitive for most colony worlds, the lack of potable water tended to discourage new exploration. In 2177, however, entrepreneur Rudolph Ryan patented a process for transforming interplanetary tankers into FTL-driven "iceships" able to quickly transport huge icebergs across interstellar space. Within a few short years, the Ryan Cartel became the single most profitable enterprise within the Alliance, and its iceships stimulated the colonization of many worlds previously believed only marginally habitable.

With each expansion of human-occupied space, the time needed to transmit messages to and from Terra also increased, making it difficult for Parliament to administer colony worlds directly. This forced the Alliance to delegate more authority to its appointed governors, who, in turn, had to grant extensive home-rule authority to colonists. When a coalition of colonies along the outer reaches of known space declared its independence in 2355, there began a bitter, 18-month battle with Terra, which became known as the Outer Reaches Rebellion. Much to its surprise, the Terran government lacked both the military resources and the political support needed to crush the rebellion.

The loss of these rebel worlds set off a political crisis within the Alliance that ultimately resulted in a vote of no-confidence against the ruling Expansionist Party. Upon taking power, the new Liberal government withdrew Terran troops and administrators from all frontier worlds, granting the colonies independence, whether they wanted it or not. This isolationist policy soon proved just as unpopular as expansionism because of the resulting political turmoil and economic upheaval. By 2242, the boundary of Alliance holdings was no more than 30 light years from Sol, a single jump by an FTL- ship. For the next 70 years, neither major political party was able to establish parliamentary control on Terra, and their respective regimes alternated, falling as quickly as they rose.

To escape the constant political unrest and economic hard times, many of Terra's best and brightest began to migrate to the now-independent colonies during the latter half of the 23rd century. Later historians dubbed this period "the Exodus." Terrans colonized more than 1500 new planets during the Exodus, extending the borders of human-occupied space to more than 150 light years from Sol. With more and more of Terra's resources devoted to colonization, scientific research lagged. On the struggling colony worlds, too, the colonists were too pressed with the problems of survival to think much about developing new technology.

Meanwhile, some of the ex-colonies were attempting to consolidate their independence by banding together for mutual support. In 2271, the Treaty of Marik was signed by three minor heads of state. Thus was born the Free Worlds League, the first of the great federations that would one day vie for power and dominion over all the rest.

Consolidation (2314-2398):

The Terran Alliance ultimately collapsed beneath the weight of its own discontent in September 2314. When a short, vicious war broke out between rival Expansionist and Liberal factions, Fleet Admiral James McKenna intervened with Alliance military forces to halt the conflict.

McKenna was a proud, charismatic career officer with a spotless military record and a long family heritage of service to the Terran Alliance (and the Western Alliance before it). He was the archtypical hero, appearing at a critical juncture and turning the tide of history in a new direction. McKenna was determined to restore his native Terra to its former proud position as leader and progenitor of "Homo stellaris." After dissolving the Alliance, he declared himself ruler of a new state, the Terran Hegemony. Under his leadership, the Hegemony embarked on an active and campaign to restore Terra's political control over its former colonies.

By the time of McKenna's death in 2339, the Hegemony had used military, political, and economic means to reassert its authority over more than 100 worlds.

In 2340, Michael Cameron, McKenna's nephew, was elected to succeed his uncle as Director-General. During Cameron's term of office, the Hegemony engaged in an ambitious government-sponsored research effort. The first significant product of these efforts was the development of a prototype WorkMech, a fusion-powered mining vehicle that reproduced body movements through artificial muscle structure based on the myomer technology developed back in the 21st century. The reemergence of Terra as both a political and scientific force created a new era of detente and relatively peaceful development for the whole human sphere.

Starting with the Crucis Pact of 2317, a number of mutual-defense leagues and trade agreements similar to the Treaty of Marik were signed among worlds. Although most of these agreements granted member-worlds total sovereignty over internal matters, they also allowed more developed colonies to control poorer, younger neighbors. By the time the Hegemony and other states of the Inner Sphere undertook the Grand Survey of 2389, ten separate states with strong central governments had emerged, each controlling worlds within communications range of their capitals. Six strong states had emerged in the "Inner Sphere," and other, smaller governments had sprung up at the fringes of colonized space, now known as "the Periphery." There were, however, frequent disputes over border worlds, especially those with ample water or mineral resources. This tended to make the boundaries of the various states a matter of tension or even war. As confrontations over these planets grew more frequent, an arms race followed, further exacerbating tensions throughout human space.

Though the other federations and states tried to follow the lead of the Hegemony in supporting new research facilities, most lagged behind. In one respect, however, the other governments mirrored the Hegemony absolutely: the creation of a hereditary leadership, embodied in a single ruling family. Commenting on this, social historians have argued that the dynastic form of rule probably offered a comforting reassurance after the chaos of the Exodus years.