The details of the Old Federation are not extremely relevant to the modern day. They lived, they died, and now we sometimes take their stuff and sell it to militaries for mad bank because no one out here has the factory to make new versions. But I felt like typing it up, and it's not really a spoiler, so I figured I may as well post it here in case anyone else is interested.
The East Asian Alliance (EAA)
Throughout the late 20th and early 21st centuries, the People's Republic of China and the Republic of India were a growing economic power on Earth. The two, along with other major economic powers of the time like the Russian Federation, the United States of America, and the Federal Republic of Germany, began coming precariously close to armed combat with one another over control of resources. Ultimately, the governments of China and India realized that if they could not match the power of the united front presented by the North Atlantic Treaty Organization, a losing war against NATO would be all but inevitable. To that end, they and a few other minor nations from the Siamese Peninsula and central Asia formed the East Asian Alliance. Now facing a united enemy, NATO abandoned its plans for war, and instead refocused their resources on searching for untapped exploitable resources in space.
While the nations of NATO had a significant headstart in terms of economic power, they were also suffering under a crippling shortage of labor as their aging populations failed to reproduce enough to replinish the workforce. The EAA, whose members were, if anything, confronted with the opposite problem, had the manpower to build an extensive mining operation throughout the Sol system. Thus it was they who discovered the Deutrion in Sol's asteroid belt, and for many years held a monopoly on it. It wasn't long, however, before NATO also established mining operations in the belt, and unlike the EAA, they had the scientific expertise necessary to create the warp drive. Thus, in the early 22nd century, NATO became the first to create interstellar colonies on Alpha Centauri, terraforming Alpha Prime in order to be suitable for human habitation.
Throughout the first half of the 22nd century, EAA and NATO would create vast colonial empires throughout known space, and in turn these colonies eventually revolted. NATO's holdings in Sirius and Alpha Centauri broke away, and EAA was eventually forced to relinquish Tau Ceti to separatists, however fortress systems like Barnard's Star and Wolf 359, as well as minor colonies like Eridani 40 and Ross 248, remained primarily under the control of the two Earth factions. In the year 2169, Earth became the only planet to host two separate members of the Interstellar Federation, as both EAA and NATO took seats on the council. However, with the advent of the Deutrion Wars just a few decades later, war returned to Earth for the first time in nearly a century as forces from FRAC and STU poured into the Sol system, seeking to seize their vast Deutrion reserves and use them to bolster their own economies, which were slowly but steadily running out of Deutrion altogether. Bound tighter together by the Deutrion Wars, the differences between EAA and NATO would eventually be done away with altogether in the year 2203, being replaced de jure with the Unified Congress and Navy of Sol (UCNS), the officers of which had already been running the system de facto for over a decade.
The Free Republics of Alpha Centauri (FRAC)
When Alpha Centauri was colonized, the member nations of NATO were still largely independent from the sovereignty of the organization, and thus when they collectively began to colonize the Alpha Centauri system, the colonies were administered separately. As the 21st century bled into the 22nd, however, and NATO became both more unified and more concerned with growing its interstellar empire and defeating its rival, the EAA, the colonies of Alpha Centauri found themselves struggling under increasing demands on their resources, and were often dragged into wars with Tau Ceti or EAA holdings in Sirius. Smaller nations began breaking away from NATO control altogether, and ultimately the larger nations followed suit. What followed was an almost decade-long struggle for independence, funded primarily by EAA, which finally ended when NATO began to fear that the war might drain enough of their resources as to make their holdings in Procyon and Sirius, or possibly even in Sol, vulnerable to EAA's military proper. Thus, in the year 2116, the colonies of Alpha Centauri became the first major independent nations located outside the Sol system. For the sake of mutual defense, they soon formed the Free Republics of Alpha Centauri (FRAC), a system-wide alliance that did little to regulate its members domestic policies, but who stood united against invasion from without.
Alpha Centauri became an increasingly powerful third party to the empire building of NATO and EAA, starting up colonies of their own in the rim systems, and fighting not infrequent wars with both NATO and EAA, often in support of other rebelling colonies like the Republic of Procyon (RoP) or the Sirius Trade Union (STU). When these wars were finally laid to rest by the formation of the Federation, recognizing the rights of all existing independent systems and vowing to put an end to war in space, thus freeing the new colonies from the destruction and extortion these wars brought, FRAC became an economic power on par with that of the nations of Sol. When the Deutrion Wars followed not long after, FRAC and STU comprised a powerful alliance against Sol, however relations between the two broke down after initial successes in the invasion of Sol, and before they could go forward with the invasion of Earth, they devolved into war with one another, allowing NATO and EAA (now effectively acting as one) to retake their lost holdings.
As the Deutrion Wars neared their end, FRAC broke down entirely, its member nations turning on one another, and its united military falling into civil war as different officers sided with different nations. Although Alpha Prime would ultimately recover from this chaos and re-establish a planetary government similar to FRAC, Mengsk and Trios remain in a state of perpetual chaos.
The North Atlantic Treaty Organization (NATO)
When the dust finally cleared from World War II, the most devastating war ever visited upon Earth, two nations were left as the first global superpowers. The Union of Soviet Socialist Republics (USSR) and their allies formed the Warsaw Pact, while the United States of America (USA) and their own allies formed the North American Treaty Organization. Thanks to the recent advent of nuclear weapons, the two would never come into direct military conflict with one another, instead funding a number of proxy wars around the globe. In the end, poor economics in the USSR's homeland saw it dissolving, and taking the Warsaw Pact with it. In the years to come, the nations of NATO, particularly the USA, would become the only remaining economic and military superpowers. The economy, if not the government, had been globalized, leaving the majority of Earth united, however tenuously, by a single supply chain which, if broken, would bring all nations to ruin.
Nevertheless, war threatened, and in order to provide a powerful enough military to act as deterrent, the People's Republic of China, the Republic of India, and their allies would ultimately form the East Asian Alliance (EAA). As the 21st century wore on, these two would become the premier players in an interstellar game of imperialism and oppression. Much like the European powers colonizing the rest of Earth before them, NATO and the EAA would almost never fight one another directly on Earth, however their colonies in the stars were engaged in almost constant battle with one another. The devastation and oppression that resulted from these wars, which often had little to do with the colonies own interests, led to a series of revolutionary movements, often funded by one or the other of the two interstellar powers and sometimes aided by other planetary governments who had already broken away from the nations of Earth.
Finally, in 2169, the Interstellar Federation was formed in the hopes of putting an end to the wars. Unfortunately, it was only temporarily successful. While the imperialism of NATO and EAA was successfully curbed by the Federation, short-sighted economic policy throughout known space resulted in Deutrion shortages in the former colonies, while Sol was able to live off of their existing Deutrion stockpiles, which had previously existed to fuel their war machines indefinitely during the imperial era. Facing potential societal collapse if the problem wasn't resolved and unwilling or unable to convince their populations and corporations to cut back on Deutrion consumption, the nations of FRAC and STU invaded Sol.
By the end of the Deutrion Wars, NATO and EAA had repulsed a number of attacks on Sol, and in the process had become effectively indistinguishable from one another. Ultimately, the two former empires were officially abolished and replaced with the United Congress and Navy of Sol (UCNS), which continues ruling over the system with an iron fist to this day.
The Republic of Procyon (RoP)
Procyon was originally colonized by NATO and rapidly became their premier weapons manufacturing system. Because of this, they were regularly invaded, and would often struggle to hold Wolf 359 for NATO so as to deprive EAA of a staging area from which to launch their attacks against the system. Different parts of the Procyon system soon became resentful towards the EAA invaders, the NATO governments forcing them into the wars in the first place, or both, and while there were many attempted rebellions, some of which were immediately successful, all of them were ultimately crushed. Finally, in 2159, the Republic of Procyon broke away and took almost all of Procyon Prime with it. Supported primarily by the Sirius Trade Union rather than EAA, they were able to overcome the conflicting prejudices of the system's population and successfully broke off from NATO. This particularly violent and bloody war is what ultimately led to the peace talks that would eventually culminate in the formation of the Interstellar Federation in 2169.
The Republic of Procyon was originally an independent power in the Deutrion Wars, remaining neutral in the initial battles between Sol and the alliance between FRAC and STU, however when its own Deutrion reserves began running dangerously low, they joined STU in an attack on FRAC, and were unable to extricate themselves from the wars since then. Before long they were once again subjugated by Sol, only to have the Deutrion shortages reach a critical stage that rendered interstellar government effectively impossible. This left behind nothing but chaos in the worlds once controlled by the former Republic.
The Sirius Trade Union (STU)
Sirius was colonized by both NATO and EAA. The system soon became torn with war, with the colonies of the two empires within easy range of one another, and the perpetual warfare proved to be a serious inhibition to the development of a powerful economy in the system, despite its rich resources. In the year 2128 several major corporations stationed in the area made an agreement with EAA and staged a violent coup on Elsa and Auros, forming the Sirius Trade Union. Over the course of the ensuing war of revolution, the worlds of Minnder and Shuang were also claimed by the Trade Union, while Zhuangli, Gaia, and Mariterra remained under the control of EAA and NATO. Without the support of many of its key worlds, NATO's influence in the system rapidly faded, and EAA seized control of all worlds not already members of STU.
War between STU and EAA threatened on occasion, but ultimately never came about, particularly as the STU helped the EAA in repelling attacks from NATO as they tried to re-establish control over the system. The STU would go on to support rebellions in both Procyon and Tau Ceti, the latter almost pushing them to war with EAA in the Sirius system, an eventuality which was averted only because of a simultaneous invasion of EAA worlds in Sirius by NATO (this invasion was ultimately repelled). The idea of the Interstellar Federation originated with the STU as a method of putting an end to the perpetual warfare and rampant imperialism in space, and in 2169, they were successful in getting all major independent nations to sign on to the organization.
Of course, soon after they were hit hard with a resource shortage. Unable to supply energy to their citizens for much longer, they realized they would either have to take immediate and drastic action or lose their sovereignty. Uniting with the Free Republics of Alpha Centauri, they attacked Sol, seeking to steal enough of Earth's Deutrion reserves left over from the imperialism of NATO and EAA in order to buy STU enough time to find a more permanent solution to their energy problems. As they closed in on their target, however, relations between STU and FRAC broke down, and the two would ultimately go to blows. The STU was eventually responsible for bringing first the Republic of Procyon and later the CIS into the Deutrion Wars, thus ending the nations they had helped to create. Over the course of the Deutrion Wars, EAA was pushed out of the Sirius system, however STU, a loose coalition to begin with, ultimately turned on itself during the twilight years of the wars, thus resulting in a chaotic free-for-all within the system that led to a total breakdown of all planetary governments. A few remnants of the old STU remain, including Katria on planet Elsa and Dysar on Auros and Gaia, but even these are descended from STU and, thus, the Federation in name only. A series of internal coups and dramatic organizational restructuring has left the modern organizations with little in common with their original form.
The Tau Ceti Coalition of Independent States (CIS)
Tau Ceti was originally colonized by EAA in the late 21st century as they scrambled to make up for lost ground in the colonial race with NATO. Tau Ceti was rapidly developed, but tension with the motherland was almost immediate as EAA exploited the system for all it was worth in an effort to keep up with NATO's colonies in Alpha Centauri and Procyon. By the time of the triumph of the STU over NATO in 2128, Tau Ceti, which had only been settled a few decades ago, was already making plans to follow in the footsteps of Sirius. Rebellions inspired by the STU led to a domino effect, as one province after another rose up against EAA garrisons. Some of these were ultimately crushed, but with the support of the newly formed STU, the sheer number of rebellions proved to be more than EAA could handle, and in the year 2142 they withdrew from the system altogether. Fearing an invasion from NATO, the victorious rebels soon hammered together an alliance, called the Tau Ceti Coalition of Independent States (CIS). With the vast majority of Tau Ceti nations signing on to the CIS, those who resisted the Coalition, mostly opportunistic dictators or EAA loyalists, were soon crushed.
Tau Ceti then entered a period of isolationism, engaging in limited trade and no diplomacy or politicking with the other nations whatsoever. Nevertheless, invoking their aid in the revolution and their ongoing trade agreements, the STU was able to convince the CIS to join the Interstellar Federation in 2169, thus solidifying the CIS' legitimacy as a sovereign nation. Over the course of the next few decades, the CIS opened up to the other nations, but when the Deutrion Wars began, they attempted to return to their previous, isolationist ways. Ultimately, they were invaded anyways as the remaining nations sought to extract more deutrion to fuel their war machines by any means necessary. Never having been an impressive military power, Tau Ceti was barely able to survive being totally annexed during the wars. As they dropped off to an end, the battered government found itself under threat of coup from multiple high-ranking officers of its military, whose armies had ultimately developed more loyalty to their commanders than to the CIS. Compounding the problem was the fact that the CIS had never been a single nation at all, with pronounced differences between the domestic policy of different nations despite their unified opposition to external interference and their single representative on the Federation Council. Once the threat of external invasion became too improbable to hold them together, the CIS' member nations cut off all ties with one another, and with large, powerful militaries, some of which had just led successful coups against their former civilian governments, war within the CIS was inevitable. Nevertheless, it is notable that the CIS is still mostly intact, with many of its member nations still retaining the same structure and government as when the war started despite the devastation of occupation and the economic crash brought on by deutrion shortages.