The Earth Unity Government was the first global government, or complete human hegemony, in human history. The EUG was founded 90 years after the apocalyptic war between the United States of Euro-Africa and the Northern Coalition, and oversaw massive reconstruction efforts all over the Earth. The EUG also began a number of impressive construction projects that helped to usher in an era of peace and prosperity: a golden age. One such project was the construction of a massive research station--the largest ever built--in orbit of Io, a Jovian moon. It was at this research station that EUG scientists first discovered the basic principles of Warp drive, allowing for faster-than-light travel between the stars.
The Earth Unity Government's capital was located in Brisbane, Australia. The EUG was a representative democracy, whose ruling body was called the Humanity Congress.
The Earth Unity Government was founded in 2129, after a 'dark age' that lasted nearly 100 years.
By the mid-22nd century, the EUG had succeeded in rebuilding the social, industrial and economic infrastructure of Earth, ushering in a golden age of prosperity for all of humankind.
In the mid-24th century, the EUG began exploring options for interstellar travel. In 2253, the EUG launched a massive colony ship toward Sol's nearest star, Alpha Centauri, 4.37 light years beyond the Earth's own star. The colony ship was swallowed up in the black abyss between stars, never to be heard from again. In 2360, EUG researchers developed Warp drive. Early warp technology had dangerous side-effects for female passengers, often resulting in infertility, but the technology was finally perfected by 2391. The EUG begins exploring nearby star systems.
In 2402, a habitable planet is discovered in orbit of the Canopus star. Many other habitable planets are discovered afterwards, bringing about a new era of interstellar colonisation. The EUG establishes a "Navigation Safety Department," later called the Department of Public Safety, to oversee colonisation and commerce between the colonies.
By the late 27th century, the political dominance of the Humanity Congress began to wane. Dissatisfied with unfair congressional representation, a number of colonies rebelled against the Earth Unity Government, led by the charismatic revolutionary Carl Palgrem. The dominant force in opposition of the EUG was the Sirius colony, and the rebels quickly adopted the name Sirius Revolutionary Congress, and declared themselves independent from the EUG, thus instigating the Earth-Sirius War.
In 2689, the Earth Unity Government's Department of Public Safety launches an invasion of the Sirius starzone, occupying the colony on Sirius VI, Rondolina. The occupation army is extremely undisciplined, resulting in a brutal occupation, eventually culminating in a massacre of thousands of civilians in Rondolina's capital city, Laglane.
By 2689, the Sirius Revolutionary Congress succeeds in liberating Rondolina after winning a series of astonishing victories against the undisciplined forces of the EUG's Department of Public Safety. After driving the EUG navy from Sirius, Carl Palgrem's Black Fleet proceeds to Earth itself, initiating a two-month-long blockade of the planet. Weakened and starving from the blockade, the Earth Unity Government was unable to defend itself when the Black Fleet descended on the planet, bombarding the Earth leaving one billion survivors. most of them left for other planets.
Shortly after the destruction of the Earth Unity Government, the Sirius Revolutionary Congress collapsed. The various colony worlds each fight each other for control of space, but are unable to establish a single, cohesive government. The isolated colonies of Earth become little more than a a mass of independent city-states.
One of the key components of Terraism, the ideology behind the Earth Cult, was the re-establishment of the Earth Unity Government--the creation of a new hegemony of humankind, reaching out across the stars, with the charred husk of Earth as its centre. It is possible that the initial roots of Terraism were a desire to take revenge upon the colonies that had done such terrible things to humanity's home planet.