The United Universal Republic, often referred to as the UUR, The Rebellion to Empire forces or just simple "The Republic" is one of two superpowers the Thousand-Year War focuses on, the other being the United Empire of Humanity (Also known as the Terran Empire).
Accepting of all races in the galaxy, the Republic seeks to bring peace to the galaxy by united all the races of the universe under one banner.
After the Secession, the Rebels, formally referring to themselves as the United Universal Republic, formed a senate comprised of Human and Sophon diplomats.
The Senate was trusted with making crucial decisions on behalf of the Republic as a whole, which they soon realized was an incredibly difficult thing to do with trillions of people in a democratic society.
In 3677, the Amoebas empire joined the Senate after one of their home planets was saved from an invasion by the Terran Empire. Unfortunately, the proximity of the Amoeba planet meant that the Terran Empire was coming very close to Republic territory.
Because of this, the Republic had to move the Senate to Apophos II, several star systems away. The Madrigal system, formerly the prosperous home world of the Republic, was now the front lines.