Guardian Units of the Nations

The Guardian Units of the Nations, also abbreviated as GUN or G.U.N., is an organisation that appears in the anime series Sonic X and its comic series. It is a military organization, affiliated with the President, armed with their expertise in warfare in order to protect humanity and maintain peace on Earth.

Early history
Around fifty years prior to the events of Sonic X, GUN was called to deploy troops to Space Colony ARK in order to stop Project Shadow, a research project led by Professor Gerald Robotnik that aimed to create the "Ultimate Lifeform" because the government deemed it as a threat. They apprehended most of the researchers (except for Gerald, who would be taken to Prison Island to be sentenced to execution) and stopped their research projects, sealing the prototype of the Ultimate Lifeform away in the ARK. Maria, who attempted to release the completed Ultimate Lifeform (Shadow), was also killed. GUN would later shut down the ARK for the next fifty years.

New World Saga
Following the arrival of Sonic the Hedgehog, his friends and Dr. Eggman, GUN grew suspicious of the new inhabitants and in particular, Dr. Eggman, for his world domination schemes.

Area 99
Area 99 is the first military base as well as a research facility. Its first experiment was to examine the captured Cream and Cheese although Sonic rescued them from the facility.

Trivia

 * In the English dub of Sonic X, G.U.N. is not referred to as such in the whole series. This is most likely due to "GUN" sounding similar to gun as in the projectile weapon. However, "G.U.N." is still mentioned in the brief synopsis of some Australian Sonic X Volume DVD covers which had episodes that G.U.N. appeared in.