At first, the government on Coruscant wished for slow expansion, despite its promotion of hyperspace exploration. However, against the government's wishes, the membership of the Republic boomed for its first millennium of existence, mainly due to worlds wishing to join as protection against the Hutt Empire.

For years, the Jedi Knights and the ancient armies and navies of the Republic defended against violence. Around 24,500 BBY, the First Great Schism occurred, after the Legions of Lettow were established by dissident Jedi who believed that true power was achieved not through passive meditation, as taught by their Jedi Masters, but through emotion. The tension between the Jedi and these dissident Fallen Jedi, led first by Xendor, and then after Xendor's death, by Arden Lyn, grew until conflict erupted.

In 24,000 BBY, the Republic entered into a war with the Honorable Union of Desevro & Tion. The war traveled up and down the Perlemian, and the respective capitals of Coruscant and Desevro both suffered volleys of pressure bombs. The Republic eventually won the war by stirring up the Hutts against the Tionese. Within a century, most of the Tion Cluster swore allegiance to Coruscant, except for Desevro, which chose to remain independent.

During the Great Manifest Period (20,000 BBY–17,000 BBY), the Republic expanded eastwards across the galaxy. Despite this, the Slice would remain the heart of navigable space. Eventually, the Republic expanded past the galactic-northern and -southern borders of the Slice, though most of the galaxy was still unknown, except for outposts such as Ord Mantell (12,000 BBY) and Malastare (8,000 BBY). The space west of Coruscant still remained unexplored since analogues to the Perlemian Trade Route and the Corellian Run in that direction still had not been discovered. Worse, progress was limited to dangerous one- or two-light-year jumps into a stretch of hyperspatial anomalies. During this period, the Expansion Region was formed. However, this region suffered greatly as a result of the Alsakan attempting to snatch control of the Republic from Coruscant. This resulted in seventeen Alsakan Conflicts, spanning from 17,000 BBY to 3,000 BBY. However, most of the fighting took place between their holdings in the Expansion Region, rather than in the Core itself. Needless to say, Coruscant won every conflict it fought.

During this period, the First Arkanian Conflict also took place. The Arkanian geneticists also began a series of genetic experiments of other sentient species, most notably bundling away several six-armed Xexto from Troiken, and transforming them into a new species known as the Quermians.

In 15,500 BBY, after a disastrous first contact, Coruscant was assaulted by Star Dragons in the Duinuogwuin Conflict. The conflict was peacefully resolved by Supreme Chancellor Fillorean and the Star Dragon philosopher Borz'Mat'oh, who together founded the University of Coruscant. At some time prior to 12,000 BBY, the Galactic Museum was established on Coruscant.


The Senate Hall.Around 12,000 BBY, Contispex became Supreme Chancellor. He and his descendants belonged to the theocratic Pius Dea cult that would control the Republic for the next 1,000 years. These fanatic Supreme Chancellors sanctioned "crusades" against rival alien sects in the Rim. After 11,000 BBY the cult may have violently dissolved. The tensions from the fallout of the crusades would deepen the rifts between the Core Worlds and those of the Rim, which Emperor Palpatine would exploit during his reign millennia later.

Around 9,000 BBY, Blotus the Hutt became Supreme Chancellor and ruled the Galactic Republic for 275 years during the Rianitus Period. Unlike most other Hutts, Blotus was a distinguished and just ruler. At least by 7,308 BBY, the Galactic Standard Calendar was fixed.

In 7,003 BBY, the Second Great Schism occurred when a group of fallen Jedi discovered a Force technique that could alter lifeforms. This started the centuries-long Hundred-Year Darkness, which saw the creation of monstrous creatures, most notably the serpentine Leviathans, which drew life-energies into blister-traps on their backs. At the Battle of Corbos in 6,900 BBY, the Jedi crushed the rebellion and banished these fallen Jedi from known space. However, the fallen Jedi discovered Ziost, a desolate world inhabited by the relatively primitive but unusually Force-sensitive Sith people.

Using their training in the Force, the fallen Jedi amazed the Sith and elevated themselves to god-like status on nearby Korriban, becoming the rulers of the Sith people. As years passed, and interbreeding occurred between the fallen Jedi and the Sith, the term "Sith" came to mean not only the original inhabitants of Korriban and Ziost, but also their fallen Jedi masters.


Coruscant, the Galactic capital, assaulted during the Great Hyperspace War.In 5,000 BBY, the Jedi and the Sith Empire clashed in the Great Hyperspace War. Many worlds were forever scarred in that battle, but the Jedi were able to repulse the invaders. After that, the Republic granted the Jedi land over a Force nexus: a sacred mountain on Coruscant.

In 4,250 BBY, the Third Great Schism occurred, which involved fighting on Coruscant. The surviving Dark Jedi were forced to flee to the Vultar system, where they discovered ancient technology indicating that the system's worlds were artificial constructs, probably the creations of the mysterious Celestials who had also built the Corellian system. These Dark Jedi took over these machines, including the Cosmic Turbine, but could not control them, and soon destroyed the whole system and everything in them during the Vultar Cataclysm. In 4,019 BBY, four Jedi Masters (two Warrior Masters and two Sage Masters) established the ziggurat of the Jedi Temple over the Force nexus on Coruscant, which would stand for over four thousand years.

The year 4,015 BBY saw the Great Droid Revolution on Coruscant, led by HK-01, who was eventually defeated by Arca Jeth and the Jedi. During the conflict, Arca Jeth discovered techniques for disabling machines through the use of the Force.

Following those conflicts were those of the Old Sith Wars of c.4,000 BBY which almost destroyed the Republic. During the Great Sith War (4,000 BBY–3,996 BBY), the Sith Lords Exar Kun and Ulic Qel-Droma, along with their Krath and Mandalorian allies, waged war on the Republic, causing devastation until they were defeated by the combined Jedi and Republic forces. Afterward, the Great Hunt (3,995–3,993 BBY) and the Cleansing of the Nine Houses occurred.

These would be followed by the Mandalorian Wars (3,966—3,960 BBY). They were fought between Mandalorian forces hoping to expand their colonies beyond the Outer Rim Territories and the Galactic Republic, which feared further incursions. The Mandalorian Wars were a prelude to the more devastating Jedi Civil War (3,959 BBY–3,956 BBY). The Jedi Civil War, also known to some as the War of the Star Forge, was fought between the Republic and the Sith Empire under Darth Revan and Darth Malak. It was possibly the most destructive conflict of that entire era, with many worlds, including Taris, Dantooine, and Telos IV, being devastated by the Sith fleet.