The United Federation is a government that governs most if not all Human and Overlander settlements and inhabited areas on Mobius. Its capital is Central City, and its primary military force is G.U.N.. The United Federation, which is run by the President, was responsible for the nuclear strike which destroyed Robotropolis. Recently, the United Federation and the Kingdom of Acorn have been engaged in all-out war with the Eggman Empire.
Prior to becoming part of the United Federation, the city of Station Square and several other hidden cities remained isolated for thousands of years, having been formed by different groups of humans who survived the Xorda's destructive attack on the planet, eventually communicating with one another and forming the United Federation. (StH: #106, CSE)
Over time, a formal structure came to the organization. Each city was designed to act as its' own country and have a unique form of self-government complete with unique types of rulers. Each ruler represented their city-state and served as a council to the President of the republic, who presided over Central City. To protect the other city-states, if one was discovered, it would act as if they were the only group left of the old world. All city-states were designed to turn to its' united task force: G.U.N. in times of defense. The leader of G.U.N. could only answer to the president. (SSSM: #2)
Station Square and the United Federation did eventually make contact with their genetic cousins: the Overlanders. The Heritage Project was implemented which allowed both humans and Overlanders a chance to come into the others' worlds and expose their cultures to each other. At the end of the Great War, one-third of the Overlanders were allowed to immigrate to the Republic of Station Square, one of them being the future Commander Tower. (SSSM: #2)
Following the incident involving the water beast Chaos and the visit from the Knothole Freedom Fighters, Station Square abandoned its isolationist policy and over time the rest of the United Federation became known as well. After a large group of Overlander families immigrated to the city of Station Square, the government increased its spheres of influence, developing colonies in the surrounding areas and getting all the overlander cities to join it mostly by peaceful means, thus uniting all humans and overlander under one rule. (StH: #80, #81, #106, #107, #162)
War with Eggman Empire
Following the Xorda's return and their second attack, the United Federation developed closer ties with the Kingdom of Acorn, forming an official alliance with them against the expansionist Eggman Empire. (StH: #130)
The United Federation sent an expeditionary force of G.U.N. troops to aid the Mes Braves Battalion and Chaotix in defending the dome shield surrounding the radioactive wastelands of Robotropolis. (StH: #131, #132, #133)
The United Federation later hired the assistance of the Chaotix to investigate the newly contructed Casino of Renfield T. Rodent, which turned out to be a front for one of Dr. Eggman's Infiltrator factories. Upon this discovery, Renfield was put on trial in Station Square courts. (StH: #166)
The United Federation currently consists of all the human and Overlander settlements and territories, at least a half-dozen Mobian city-states with it, its capital of Central City, with Station Square, Soleanna, Westopolis, Spagonia, Empire City, Chun-Nan, and Mazuri also part of the United Federation. (StH: #200, CSE)
Each city within the United Federation acts as its own independent country, and represents a different style of self-government. Each leader represents their city-state and serves on the President's Council. (SSSM #2)
- It is possible that the city of Shamar from Sonic Unleashed also existed in the Pre-SGW timeline. It is mentioned in the Sonic Super Digest that Professor Pickle hails from the University of Spagonia and the University of Shamar. However, it is not yet clear if this is canon.
- The UF flag is actually not new, as you can slightly see it the Shadow the Hedgehog game at the front and in office of the President's House.