Guardian Unit of Nations 

Alias: G.U.N., Gun and Military shadow ops program

Alignment: Good

Resident location/or bases:

Headquarters

Type: Military Force

Time of formation:

Unknown iterations

Allies:

United States

Team Sonic:

Knuckles the Echidna

Miles "Tails" Prower

Sonic the Hedgehog

Neutral:

Union Academy

Union Council

Atlas Army (Rival)

Enemies:

Eggman Empire

Team Robotnik

League of Darkness

Black Arms

Members:

Commander Walters (founder and former leader) (deceased)

Commander Abraham Tower (second in command and new leader)

Rockwell (director)

Vali team (GUN Undercover Agent):

Vali Lucifer

Biku

Kuroka

Arthur Pendragon

Fenrir

Le Fay Pendragon

Gogmagog

Shadow the Hedgehog

Rouge the Bat

Team Dark

others agents 

Info: The date of the foundation of the Guardian Units of Nations is unknown, whether due to rise of superheroes or maybe due to extraterrestrial lifeforms. The Guardian Units of Nations led by Commander Walter put in charge alongside Commander Abraham Tower into a global task force to deal any extraterrestrial threats on Earth like Eggman make threats mankind or the League of Darkness.

For Union Academy, the GUN consider to be useful allies while Atlas became formidable rival despite Union City set in Japan. The GUN HQ located in London, UK despite Commander Walters originally as American alongside Abraham Tower. GUN branches expanded across the globe such as Asia, Europe, America and Africa.

Fifty years ago, when the government of the United States began fearing the results of Project Shadow, directed by Professor Gerald Robotnik onboard the Space Colony ARK, the top officials of G.U.N. at the time saw the research institution's uniqueness as hostile, and arrived at the decision to set a plan to close the ARK itself. Making up a public story that a biohazard outbreak had occurred within the ARK, the military formulated the so-called "ARK Seal Operation", whose purpose was to close down he spaceship's research facility, destroy everyone and everything (except Gerald) related to the project, and detain the professor as the cause of the accident. When Project Shadow was completed, the ARK was violently invaded by G.U.N. Soldiers, evacuating civilians and killing researchers. During the attack, Gerald put his finishing touches on his research's final result: Shadow the Hedgehog, the "Ultimate Lifeform" and the "Ultimate Fanus". Robotnik then had him escape to safety with his granddaughter, Maria. In the ensuing chase, the two got to the escape pods, but Maria was shot by a soldier when helping the hedgehog escape. Mortally wounded, she ejected her friend to earth in a pod.

Within a week, the residents of the ARK had all been moved back to ARK, the space station's research facilities had been frozen, and the people involved in Project Shadow, except for Gerald, were announced as victims of the accident told to the public. Meanwhile, Union Headmaster felt aware with the GUN doing so call accident, they remain a mystery because they shouldn't participate with GUN since the GUN denied sending them to the ARK it will risk of loosing heroes. The plan was completed when the project's prototype, the Biolizard, was sealed away onboard the ARK after finding it in the deepest part of the spacecraft. The ARK was then sealed off, probably to prevent the Biolizard from falling into the wrong hands.

When the operations about Project Shadow ceased on the ARK, Gerald was taken to Prison Island  to continue his research under military control. G.U.N. later retrieved Shadow and brought him to the island for Robotnik to continue his work, but when the professor learned that Maria had been killed, he went mad with grief. While it was thought that he was continuing his research with the black hedgehog, Gerald secretly created a program that would cause the ARK to fall to earth and destroy it as his revenge at Humanity, going as far as to brainwash Shadow to make him carry out his revenge when he awoke. When G.U.N. began to fear how the professor might retaliate, they incarcerated him. Knowing only the danger of Project Shadow, the military sealed Prison Island and abandoned Gerald's research. Robotnik was subsequently executed while Shadow was placed in suspended animation on the island. 

At some point after Project Shadow's end, G.U.N. began using the Chaos Drives - crystallized Chaos Emerald Energy developed by Gerald - to power their machines. In no time, most of their armed forces began consisting of highly advanced, automated robots powered by these Chaos Drives. The GUN's advanced machine powered by Chaos drives began formidable source than Atlas military mech AKs and Paladin.

In present day, the League of Darkness Vali team (undercover agent of GUN) alongside League of Villains and Phantom Task ordered by League of Darkness themselves, to infiltrate the Prison Island to find an energy source. Later, the group encountered the mad scientist, Dr Eggman, soon he explained to them about the project called Project Shadow when they came across Eggman's grandfather's diary by sheer coincidence. Coveting the "Ultimate Lifeform" for his own use, the doctor alongside League of Darkness raided Prison Island and broke into G.U.N.'s underground base there. After overcoming the various hordes of military robots defending the facility, the scientist awoke Shadow, who showcased his power by destroying a G.U.N. B-3x Hot Shot mech in less than then seconds.

Mistaking Shadow for Sonic the Hedgehog, G.U.N. found the latter the next day. Seeing him as a deserter from the military facility, they caught him and were about to take him to Prison Island. However, when the Sigma-Alpha 2 helicopter containing Sonic was flying over

 San Fransico, the rather rebellious hero broke out and fell into the city down below, where he evaded the various troops hot on his heels. Eventually, G.U.N. sent out their one of their massive military trucks to chase after the hedgehog, but this mission was unsuccessful. That night, Shadow stole a Chaos Emerald from the national reserve bank and ran through the capital city while the military was hot on his heels. Meanwhile, the armed forces had a F-6t Big Foot mech attempt to defeat Sonic, but they saw little success. However, when the blue hedgehog met the black hedgehog alongside Vali team aside with him, soon after and the latter left using Chaos Control, G.U.N. finally caught the hero and imprisoned him on Prison Island.

The next day, G.U.N. met even more interference from Tails, Amy, Sonic's friend and Union Students who wanted to liberate him. While the fox made his way through Prison Island's base, overcoming the troops protecting it, Amy and Ruby infiltrated the prison and broke Sonic out.  In the meantime, Eggman would return to the island with Shadow and Rouge the Bat and League of Darkness, having the former plant Eggman Bomboms, throughout the facility to destroy it and the latter infiltrate the military base to get the three Chaos Emeralds.  there. Soon after, Sonic would escape to the Green Forest, where he found the black hedgehog yet again but Vali team and League of VIllains were there too, Sonic got his allies, Rias and her peerage and Izuku and his class 1A. After a fight between the two hedgehogs, heroes and villains that ended in a stalemate, it was revealed that the planted bombs were about to go off in a minute and a half, which would destroy the entire island. As such, Shadow warped himself and Rouge out of Prison Island, while Sonic found Tails, Amy and Union Students narrowly escaped with them as the facility was destroyed.

That night, when Eggman made his threat to the United States and world leaders including Union Academy to surrender  in the next twenty-four hours, G.U.N. troops would chase after Tails while he was making his way through the capital city to pinpoint the doctor's location. At some point following this, G.U.N. dropped the charges against Sonic and the others.

G.U.N Soldier

Weapons:

Energy-based assault laser rifle

Motor Vehicles:

M1 Abrams

M113 Armored Personnel Carrier (APC)

MIM-72 Chapparral

LAV III

HMMWV

Aircraft

AH-64 Apache

SB-1 Defiant

Bullhead