Earth Defense Council

The Terran Alliance, sometimes referred to as the Alliance, was the ruling body of the Earth (84 BBY - 14 ABY) and, eventually, the entire Sol system (20 ABY -). The Alliance, led by its Potentate, lasted over a century before falling to the in 14 ABY, but was restored six years later when it fought what was left of the Imperials off-world. It was a self-described democracy.

Formation
At one time, Earth had many primitive nations living in various areas of its seven continents. For thousands of years these nations appeared and disappeared, all of them leaving significant marks in the planet's history. Sometime around 90 BBY, the Humans that inhabited the planet had caught up with the technology levels found in the the galaxy far, far away. In a violent war, the Earth was ravaged, but by 84 BBY, the war had ended, and the various nations united to form the Terran Alliance. This Alliance would still be around ninety-five years later when the Imperial Remnant first "discovered" the planet.

Government and politics
The Alliance's government was originally formed in the aftermath of a great war between several of the planet's many nations. It unified all of Earth's governments into one, and promoted peace and democracy planet-wide. It was controlled by a senate and courts system, with a Potentate in the position of the executive branch.

Military
The Alliance officially began building its army and navy in 84 BBY, several months after its founding, in fear that it might encounter alien species within its own system and galaxy. Its military would serve and evolve for nearly a century before seeing any real combat; when the invaded the Sol system in 11 ABY.

The Terran military was surprisingly modern by Imperial standards and fought the Imperials to a standstill, and eventually beat them in 21 ABY.

Behind the scenes
The Alliance is finds much of its basis in the ideas of a "New World Order", as well as the unified Earth government in the Halo video games series.