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 permanently 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.