At first, the Galactic Republic had no idea where this mysterious mechanical species had come from or what its purpose was. They did not even know its name. Only later, during several clashes between the two fleets, did they intercept some of the other side's communications. After careful decryption, they found the repeatedly appearing word "Geth" and finally learned that their opponent called itself the Geth.
After the initial few encounters, the Galactic Republic's small local Defense Fleets were no match for the Geth fleet. Many colonies and planets fell.
The Geth fleet was not numerous, and its warships were not particularly large. But that was because their warships had no need to account for life-support systems. Every member aboard was a mechanical unit; indeed, the warship itself was a gigantic mechanical unit. Their level of automation was extremely high, so a Geth warship of the same size possessed at least five times the combat power of a Republic warship!
The Galactic Republic's first contact with the Geth came after the InterGalactic Banking Clan and the Fourth Group fleet raided Janfatar. That battle was interrupted by the Geth's large-scale appearance. Afterward, Jedi Master Sass Tiin, who had led the Republic fleet there, engaged the Geth in a direct confrontation.
But in that clash, Sass Tiin was utterly unfamiliar with the Geth and never expected them to resort to schemes and deception. He was defeated.
After that, Sass Tiin naturally became an adviser to the Galactic Republic's Eighth Army, specializing in combat against the Geth.
At the same time, the Galactic Republic's various departments began debating the Geth's origins.
Through continuous hyperspace scans, the Republic roughly determined that the Geth fleet's operations had a center, located in the Northern Galaxy, on a planet at the outermost edge of the Eighth Army's