Overview

 Featuring a space opera setting, the main storyline revolves around a war between three galactic species: the protoss, the zerg and the terrans Below is a brief history on how these factions came to contact with one another.

Protoss

The protoss were discovered by Amon and his followers on Aiur, a world the xel'naga had previously engineered. The xel'naga, who were nearing the end of their life cycle, were in need of a race to achieve purity of form and intrigued by their mental connection, chose to use the protoss. Amon uplifted the protoss and manipulated their essence. Pushing the evolution of the protoss, the purity of form was achieved and the xel'naga eventually descended to Aiur. The protoss, who revered the Amon and his followers as gods, learned much from them. But in time, they began to grow wary of their creators, and rebelled from them, attacking their ships and killing hundreds. Amon and his followers left the planet as the protoss fell into the Aeon of Strife, a period of brutal civil war. Until the End War, history would hold that it was the xel'naga as a whole that were responsible for this uplift.

The destructive civil war ended when Khas, using xel'naga-derived artifacts called khaydarin crystals, re-created the psionic link. It became the basis of a new philosophy called the Khala.

Approximately 1500 by terran reckoning, the Conclave attempted to exterminate rogue heretics who had deliberately cut themselves off from the Khala and would later become known as the Dark Templar. They ordered Executor Adun to execute them, but Adun refused, instead teaching the rogues to hide from the Conclave. Eventually the rogues lost control of their powers, alerting the Conclave. They were secretly banished on a xel'naga ship.

By 2499 the protoss became aware of a xenomorphic threat, the zerg, another alien species also created by the xel'naga. The zerg were attacking the terrans, a species which had traveled to the Koprulu Sector two hundred years previously. The Conclave dispatched Tassadar and a force of protoss to destroy the infestation by purifying the infested worlds.

Terran

On November 22, 2229, the United Powers League was founded upon the basis of 'enlightened socialism'. It accomplished that which the now defunct United Nations never could by unifying humanity. It encompassed and controlled close to ninety-three percent of Earth's population. Only a few volatile countries in South America remained outside its fold. The UPL often resorted to fascist police actions to maintain the public order. With its control lasting for nearly eighty years, the UPL sought to unify the various cultures of humanity. It went to great lengths to eradicate the last vestiges of racial separatism and designated English as the common language of Earth, banning many ancient languages in their native countries.

The UPL reopened fields of research that had lain dormant for decades, including the American and Russian space exploration programs which had previously been abandoned due to drastically reduced budgets and incessant political sabotage. The coupling of cryogenic hibernation with the ability to travel through warp space ushered in a forty-year period during which the UPL founded colonies on Earth's moon and many of the other planets within the Solar system.

The prisoners were transported to Routhe's private laboratories, where he had his science crews prep them for long-term cryogenic hibernation. He catalogued their various mutations and cybernetic enhancements, then input all of the data into ATLAS, which processed this genetic information and predicted which of the prisoners should be able to survive the rigorous conditions. The forty thousand who were deemed viable were loaded onto four supercarriers loaded with enough supplies, rations and hardware to aid them once they arrived at their destination. The navigation computer was then programmed with the coordinates of Gantris VI. As these ships were intended for colonization, they included technology such as frozen fertilized eggs and embryos, cloning technology, food processors, etc.

Around 2231, ATLAS was installed into the Nagglfar. The Argo, the Sarengo and the Reagan were programmed to follow the Nagglfar as it was launched toward Gantris VI. It was scheduled as a one-year trip. At some point during the journey the navigation systems linked to ATLAS shut down, erasing the coordinates of Gantris VI and Earth. The supercarriers barreled blindly through warp space for twenty-eight years until their warp-drive engines reached critical meltdown. The supercarriers emerged into real space in the Koprulu sector. With their engines destroyed and their life-support batteries nearly exhausted, the ships engaged their emergency protocols and plummeted toward the nearest habitable worlds.

The Reagan and the Sarengo crash-landed on Umoja The Argo landed on Moria, and all information regarding their current status was erased. The Nagglfar landed on Tarsonis Thinking they were the only survivors of the Long Sleep, the inhabitants of each planet worked to survive in what they termed 'the New World', making do with whatever meager resources they could find.

Once reunited, the three colonies benefited from mutual trade and commerce treaties. The colonial populations grew quickly during the first three generations. For the first five or six generations there was social pressure to have as many children as possible The Tarsonians expanded quickly to establish cities and industry over much of the planet's surface. As the Umojans spread across the planet, they quickly adopted a method of fair and democratic governance that later became known as the Umojan Ruling Council. It had a philosophy of leaving nothing to waste In a relatively short amount of time, all three colonies spread to other worlds and developed their own prosperous, self-supporting economies.

Having founded prosperous colonies on seven other worlds, Tarsonis' military might grew by leaps and bounds. Tarsonis and its colonies founded the Terran Confederacy, which began extending its influence to other worlds. The Umojan Ruling Council was immediately wary of this. Several years later, Chau Sara and Mar Sara were colonized by an expedition from Tarsonis. Twelve major settlements were established on Mar Sara, and its mining industry was seen as a key strategic asset. However, it was always a backwater colony compared to Chau Sara, which was more prosperous

The Confederacy knew about the imminent arrival of the zerg by 2498 and experimented with captured specimens in the Jacobs Installation. They planned to use them to put an end to their rivals.

Chau Sara, Brontes and Dylar IV were infested by the zerg in 2499. On December 8, Chau Sara was incinerated from orbit by the Koprulu Expeditionary Force. As the protoss fleet made its way towards Mar Sara, the Confederacy launched a counterattack commanded by General Edmund Duke and sent a new Magistrate to safeguard the colonists and keep their state of panic from escalating any further

Zerg

The Zerg Swarm is a terrifying and ruthless amalgamation of biologically advanced, arthropodal aliens. Dedicated to the pursuit of genetic perfection, the zerg relentlessly hunt down and assimilate advanced species across the galaxy, incorporating useful genetic code into their own.[2] They are named "the Swarm" per their ability to rapidly create strains, and the relentless assaults they employ to overwhelm their foes 

Amon's xel'naga discovered the original zerg on Zerus. The fallen xel'naga directly intervened in the zerg's development to gift them with the purity of essence, making them the counterparts of the protoss, gifted with the purity of form; the zerg and protoss were intended to eventually merge to form a hybrid army for Amon. At this point the zerg species diverged into two distinct branches; the Zerg Swarm that had been altered and the primal zerg that managed to avoid the tampering of Amon's xel'naga. The xel'naga created the Overmind to control the zerg swarm and prevent a repeat of the protoss' Aeon of Strife. The Overmind oversaw the zerg swarm's rapid evolution, created the cerebrates, and divided the Swarm into broods. The primal zerg, meanwhile, went into hiding to preserve their individuality.

However, the xel'naga in Ulnar caught wind of Amon's plan, and sought to stop Amon from ending the Infinite Cycle. The two factions fought in the space above Zerus, and the swarm was released on the xel'naga. Most were slain and their knowledge was assimilated by the swarm. Through this, the Overmind became aware of the existence of the protoss, and through them sought to make the Zerg Swarm perfect. However, it was aware of the directive implanted into it by Amon, and sought ways to subvert Amon's plans