Guardian Units of the Nation

The Guardian Units of the Nation (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. It is run by Chief Commander Abraham Tower, who replaced Hugo Brass in 3237, and among its top agents are Shadow the Hedgehog, Rouge the Bat, and E-123 Omega who together form Team Dark.

Invasion of the ARK
Fifty years ago, the colonel of G.U.N. had recieved word that Project: Shadow, a project made to make immortality possible, had been a success due to Gerald Robotnik having recieved assistance from Black Doom. The colonel had his troops invade the ARK so they could use Project: Shadow as a weapon for themselves. But Shadow escaped via an escape pod thanks to Gerald's granddaughter, Maria, who was shot in the back by a soldier while trying to flee herself. The colonel then met with Gerald back on Mobius and ordered him to make a new Shadow on Prison Island, but G.U.N. could not tell if Gerald was trying to "pull a fast one" due to Shadow being so advanced and had Gerald executed. (StH: #98 #157, #171)

Capturing Sonic
One of G.U.N.'s most well 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. (StH: #98)

The Dragon Conflict
Almost a year later, Paladin Team Sigma-Alpha 2 were 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. (StH: #106, #107)

Other Missions
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. (StH: #110, #116)

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. (StH: #125)

After the Xorda
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. (StH: #131, #132, #133)

Shadow's Missions
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. (StH: #182)

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 first to the Sonic X zone, then to Blaze the Cat's world, Shadow managed to retrieve an emerald from Blaze for stopping Metal Sonic. Shadow then went back to GUN headquarters and was given his next mission. (StH: #195, SU: #1, SX: #40)

That mission was to head to New Megaopolis with Rouge the Bat and deactivate Eggman's new weapon, a laser capable of destroying the Knothole Freedom Fighters' force field, their camp, and half of the Eggdome. Shadow recruited the help of Sonic who was sleeping outside the Eggdome along with the others for the final battle. Sonic questioned why Eggman would build something so over the top, to which Shadow replied that intelligence suggests Eggman is losing his last grasp on reality. Sonic disagreed, citing that Eggman hasn't stooped that far yet. The trio tried to disable the Doom Laser, but accidentally shifted it into firing position. Shadow then took off his Inhibitor Rings and used his Chaos powers to stop the laser. He accidentally fell off the laser, but Sonic grabbed his hand, saying they're not going through the whole Shadow falling to his death a second time. Sonic then questioned if Shadow was going to join the final battle against Eggman, to which Shadow replied he owes Sonic much gratitude and the least he could do is allow Sonic to settle things with the doctor himself. (SU: #2)

Commander Tower later sent Shadow on a mission to find and possibly recruit E-102 Gamma, an old rogue E-100 Series robot who had been defeating Eggman's robots here and there, and was beginning to wear down and needed help. But Eggman was also interested in find the robot and sent out the last of his E-100 Series to find him, E-123 Omega. Shadow failed at his mission, as he and Gamma were seperated after locating him due to Omega. Omega destroyed Gamma, but E-102 gave him "brother" his free will and Omega joined GUN to follow in Gamma's steps. (SU: #3)

Shortly after this, Shadow and Rouge were sent on a mission to obtain a Chaos Emerald from the Special Zone and failed. Commander Tower then had Shadow and Rouge team up with the newly recruited E-123 Omega to form Team Dark. The trio then went to the Special Zone again, but this time accomplished their mission after resorting to Plan B. (SU: #4)

Weapons and Technology
G.U.N. employs a variety of technology and weapons, including rifles, helicopters, jets, explosives and nuclear weapons.

Background Information
The origin of their name probably stems from the Japanese word for "army" which is simply "gun" or "guntai" and then words were made to fit with the acronym.