The Guardian Units of Nations (or G.U.N.) is an elite military unit of Station Square. Its forces are made up of highly-trained military agents, field agents, and various powerful robotic weapons and vehicles. G.U.N ultimately operates under the orders of the President of the United Federation.
One of G.U.N.'s first known operations was their mission to capture Sonic the Hedgehog, when they believed he was responsible for stealing the city's Chaos Emerald. In reality, the emerald was stolen by Sonic's look-alike Shadow the Hedgehog. Although Sonic was captured by Paladin Team Sigma-Alpha 2 despite putting up resistance, he managed to escape from their helicopter while being transported to prison. Eventually Shadow's identity became known, and Sonic was exonerated for the crime.
Almost a year later, Paladin Team Sigma-Alpha 2 was once again deployed, this time to work with Sonic and the Knothole Freedom Fighters in bringing an end to the terror brought on by the dragon Zan. Sigma Alpha 2 planted the explosives in the dragon's cave that resulted in his death. In exchange for the Freedom Fighter's help and information on Dr. Eggman, Station Square accepted the numerous Overlander refugees that had been rescued from Robotropolis.
After the destruction of Robotropolis by Station Square's O.T.I.S. launching a nuclear strike, G.U.N. dispatched their Mobian agent Rouge the Bat to the ruined city of Old Megaopolis to retrieve information about Dr. Eggman's new machine body. Rouge did not return from her mission however, and G.U.N. asked for Knothole's help. Rouge was rescued by Sonic and Bunnie Rabbot, and Eggman's new robotic body was destroyed.
When the Xorda race came to Mobius and activated the Quantum Dial, G.U.N. participated in the global counter attack which included Mobians and Overlanders from throughout Mobius. The threat was ultimately eliminated by Sonic and Knuckles the Echidna.
When Sonic returned from his year-long absence from outer space following the Xorda's attack on Mobius, G.U.N. agents joined the Mes Braves Battalion and the Chaotix at Fort Acorn to prevent Eggman's SWATbots from taking down the force field around the irradiated Robotropolis.
When the Enerjak crisis emerged, G.U.N. dispatched their newest agent, Shadow, to help protect New Mobotropolis from the Chaos-demigod's wrath. Despite his best efforts however, Shadow was defeated. Enerjak was soon captured by the Egg Fleet however, and Shadow's mission was complete.
Shadow was later given a new mission to go to the Special Zone and bring back a Chaos Emerald. The young mechanic Hope Kintobor built a teleporter to take him there, but sent him to Moebius instead. After an entanglement with Metal Sonic that brought him to Blaze the Cat's world, Shadow managed to recieved an emerald from Blaze for stopping Metal Sonic. Shadow then went back to GUN headquarters and was given his next mission.
Paladin Team Sigma-Alpha 2: