The first Guardsman was Kevin O'Brien. Born in Chicago, he became an engineer and inventor working for the newly opened Lakani Island plant of Stark Industries who came to the attention of Tony Stark when he invented a stun-ray that managed to harmlessly disperse a crowd of violent protestors. Stark invited O'Brien to transfer to Stark's main plant on Long Island, and he accepted. Despite a careless streak that once caused the laboratory he was working in to explode, he became a close friend of Stark and was soon appointed head of Stark's research department.
On several occasions, O'Brien assisted Stark and his supposed bodyguard Iron Man (really Stark himself), notably against the Spymaster and his assistants the Espionage Elite, saving Stark's life on more than one occasion. Stark then decided to reveal to O'Brien that he was secretly Iron Man, and to build for him a second suit of armor for use in the event of an emergency. That emergency would come a short time later, when Iron Man and his girlfriend Marianne Rogers were taken captive by the superhuman madman Mikas the Soulfather. Putting on the armor before it was fully tested, O'Brien fell prey to a malfunction in the cybernetic circuitry controlling the armor which apparently stimulated the regions of the brain where rage and jealousy originate.
O'Brien found himself seized with sudden attraction for Stark's girlfriend Marianne Rogers, and became extremely jealous of Stark's power, looks and fortune. At the same time, Simon Gilbert, then Chairman of the Board of Stark Industries' stockholders, grew alarmed that Stark was moving out of munitions production and mapped strategies with the board to seize controlling interest in the firm from its principal stockholder, Stark himself. Clad in armor and calling himself the Guardsman, O'Brien offered to aid the board in their plot against Stark. As a show of support, he agreed to quell a protest rally outside the plant. The Guardsman aimed his repulsor rays at the crowd, injuring four protestors. Sickened by what he did, O'Brien turned on the renegade board members, physically assaulting them. However, seeing Tony Stark with Marianne Rogers caused him to once again become unbalanced, and he went outside to vent his rage on the growing crowd of protestors. Stark donned his Iron Man armor and engaged the Guardsman in battle to prevent him from doing more damage. Losing, the Guardsman sought refuge in an experimental tank. In an attempt to stop him without hurting him, Iron Man trained his repulsor rays on the vehicle and accidentally hit its fuel supply. The tank exploded, killing O'Brien.
Michael O'Brien, the brother of the original Guardsman Kevin O'Brien, was also born in Chicago, Illinois. Some months after Kevin's death, when the details of the incident came to public light, Michael, a sergeant in the New York City Police Department, decided that the official investigation exonerating Iron Man's actions was a cover-up. Reopening the investigation without official sanction, Detective O'Brien confronted Stark, interrogated several of his employees, and declared his intention of proving Stark responsible for his brother's death.
O'Brien finally hired an unscrupulous private investigator to get him inside the Long Island plant. There O'Brien located the Guardsman armor and put it on, determined to use it to bring Iron Man to justice. However, the malfunction in the cybernetic circuitry that affected his brother also affected Michael's brain, and he flew into a rage seeking to kill Iron Man. Iron Man confronted his attack and finally convinced him that the armor was causing him to act insanely. O'Brien collapsed on rebelling against his own urge to kill Iron Man. Stark took O'Brien into custody rather than press criminal charges, hoping to convince the man of his innocence in Kevin's death. While Stark worked on a new set of armor, the Japanese mutant Sunfire attacked the plant. Stark was unable to put on his new armor since it had not yet cooled, and unable to find any of his spare suits of armor since a saboteur had stolen them. Hence he was forced to put on the Guardsman armor to fight off Sunfire. O'Brien witnessed Stark's heroic attempts to save lives over a video monitor, aware that Stark was risking a major heart attack by the strenuous activity. Escaping confinement, O'Brien decided he was wrong about Stark and determined to help him by donning the now-cooled Iron Man armor. Thus clad, he was mistaken for the real Iron Man and kidnapped by the Mandarin. Stark discovered an old set of Iron Man armor that the saboteur had overlooked and went to China to rescue O'Brien. Upon rescuing him, Stark chose to reveal his true identity to O'Brien before he went off to battle the Mandarin. O'Brien flew back to New York where he took custody of the Guardsman armor once more.
After Iron Man defeated the Mandarin, Stark fixed the malfunction in the Guardsman armor's circuitry so it was safe to wear. Michael O'Brien was determined to use the armor to vindicate both his brother's and his own senseless actions. When Stark International was taken over by the criminal Midas, the Guardsman joined with a number of Stark's other friends and allies to battle Midas' men. He was turned to gold by Midas' power, but was later restored to flesh. Having quit the police force, O'Brien interviewed for the position of security director at Project: Pegasus, the government energy research facility, after its previous director, Quasar, quit. With a high recommendation by Tony Stark, O'Brien got the job. Sometime later, while guarding the Project, O'Brien's Guardsman armor was damaged in a battle with the subhuman Lava Men. It was later repaired at the Project's expense. O'Brien, as the Guardsman, has been living and working full-time in the Project since his appointment and has performed his duties capably.
Later, he was the security chief at Avengers Island. He also participated in the Iron Legion against Ultimo, wearing a re-creation of the Silver Centurion armor.Harold "Harry" Bright - member of the Vault Retrieval Team
James "Jim" Cunningham - tried not to panic during the mass breakout of the Vault
Charles "Charlie" DeMulder
Terence "Terry" Doocey
Frank Ensign (Guardsman Prime) - helped transport the Wizard to prison; later aided Iron Man (Anthony Stark).
William "Billy" Fredricks - first appeared guarding a wounded Portal in hospital and later seen at Goodman, Lieber, Kurtzberg & Book.
Patrick Herbert - worked at the Vault, was tricked by Mainframe (Ian Wajler)
Michael "Mike" Ivy - aided Guardsman Prime in the transportation of the Wizard.
Emilio Layton - member of the Vault Retrieval Team
Howard Samuels - mentally attacked by Mentallo, but survived the breakout
Gregory Smoot - was chosen to test U.S. Agent using the Iron Monger armor
Eliot Villagran - seen guarding a hospitalized Portal
Marty Delarosa - while off-duty, he met and flirted with Calypso who convinced him to sneak her into the Vault; once in, she killed him.
Larson Dzon - deceased
Curtis Elkins (Sentry) - member of the Jury and former friend of Hugh Taylor
Chris Fallon - deceased
Walt Hanna - deceased
Rick McLaurin - deceased
Ravello Medina - deceased
Corbin Rubinstein - deceased
Chuck Scott - deceased
Danny Stephens - worked at the Vault and was the first Guardsman taken hostage and killed by Venom (Eddie Brock)
Pascal Tyler - killed Cinder, framing Luke Cage and Rhino
Scott Washington (Hybrid) - also known as Guardsman 6, became known as Hybrid when the Riot, Phage, Lasher and Agony symbiotes merged with him after he was paralyzed in a gang shoot out
Both Guardsmen wore powered armor designed by Tony Stark and Stark Industries. The Guardsman armor contained a powered exoskeleton that gave the wearer superhuman strength allowing the operator to lift 40 tons under optimal conditions (for about 3 minutes). The armor's high-carbon steel alloy mesh and radiation shielding also offer protection from most ballistic and even energy weapons. The armor can fly via chemically powered boot jets at a maximum speed of 250 mph (400 km/h) for 3 hours, and contains 30 minutes air supply for submersion or high-altitude flight.
Each palm of the Guardsman armor's gauntlets contains a charged ion "repulsor ray" emitter capable of 45 seconds continuous discharge at a range of 40 feet (12 m) before irregularities in plasma cone diffuse the beam.
Kevin O'Brien had earned a PhD in engineering, with expertise in engineering and was a gifted inventor. He also used a "stun-ray" device as a weapon.
Michael O'Brien is a good hand-to-hand combatant and was coached by Captain America. As a policeman, he carried a police issue handgun, and as Avengers security chief he used "stun guns" and other advanced weaponry.
Both Kevin and Michael suffered from emotional instability that was exacerbated by the cybernetic circuitry in the original Guardsman battle-suit, causing both men to go insane. Michael O'Brien was able to wear the Guardsman armor safely after psychologically coming to terms with his trauma over his brother's death. The armor circuitry has since been modified by Anthony Stark to prevent its causing such adverse effects.
The Guardsman armor was replicated by Stane International for use at the Vault, and retained similar abilities to the original version. When the original armors were destroyed by Iron Man during the Armor Wars, Stane International attempted to re-create the Guardsman armor without Stark's designs; however, they proved inferior to the Stark-based models. Stark Enterprises replaced the second-generation Stane models with an improved design from Anthony Stark. Although superior to the Stane models, the new Stark Enterprises suits were limited to operation within the vicinity of the Vault, as a security measure to prevent misuse of their Iron Man-derived technology.The Guardsmen appear in the Iron Man episode "Armor Wars" Pt. 2. When Iron Man invaded the Vault to disable the Guardsman armors after slipping sleeping gas into the Vault's ventilation systems that puts all its inmates to sleep, he ended up in a fight with them and Hawkeye. Iron Man used the Negator Packs on them and discovered that they don't use his technology.
In the Iron Man: Armored Adventures series, the Guardsman appears in two distinct versions:
A man named O'Brien (voiced by Brian Drummond) appears as the security chief (i.e. the Guardsman's most mundane namesake) of Stark International under the personal command of Obadiah Stane, firstly in the episode "Field Trip". Although for most of his appearances he does not wear a powered armor suit of his own, he gets to pilot the Crimson Dynamo and later on the newly created Iron Monger mech to tear down a derelict city block. When, however, he refuses to finish Iron Man when the latter aids Dr. Abraham Zimmer, a resident of that area, O'Brien is fired by Stane for his act of mercy. In the episode "Iron Monger Lives", Whitney Stane briefly disguises herself as O'Brien to wreak revenge on Tony, whom she holds responsible for her father's condition.
In the episode "Armor Wars", the armored version of the Guardsman is presented as the name for a duo of criminals named Force (using repainted Space Armor) and Shockwave (using repainted Stealth Armor) appearing as public heroes and commercial mascots on behalf of Obadiah Stane. While they seem to appear just in time to prevent disastrous incidents, Pepper eventually shows Iron Man evidence revealing that the Guardsmen had in fact caused these incidents and that they are notorious criminals. At the Guardsmen Expo where Firepower (using repainted Hulkbuster armor) is unveiled as the latest member of the Guardsmen, Pepper forces the Guardsmen to reveal their identities upon hacking the Expo's television screen to show their mug shots as Maggia enforcers. After the Guardsmen are defeated by Iron Man and War Machine, Obadiah Stane escapes suspicion by claiming on television that he had no knowledge of the criminal past of the Guardsmen members.
The Guardsmen appear in Avengers Assemble. This version of the Guardsmen are robots that are based on Stark Industries' designs for the Hulkbusters. The Guardsmen first appear in "Civil War, Part 1: The Fall of Attilan" where two of them accompany Truman Marsh into arresting Inferno following the incident that Maximus brainwashed him into committing. In the episode "Civil War, Part 3: The Drums of War," the Guardsmen are shown working in the prison where the Avengers are incarcerated following their fight with the Mighty Avengers. After Tony Stark gets free and receives help from Black Widow, Black Bolt, and Medusa, they free the other Avengers and fight their way past the Guardsmen in order to get to the infirmary where Captain America is. Once Captain America is awakened, he helps the Avengers in fighting the Guardsmen until Black Bolt defeats them all with his voice where he quotes "Done."
A "Vault Guardsman" figure was released in the Toy Biz Spider-Man line under the "Techno Wars" label. The figure was derived from an unreleased figure in the Iron Man line, with removable armor plates.
A figure of Guardsman was released in wave 30 of the Marvel Minimates line.
A figure of Guardsman was released in wave 2 of Hasbro's 3.75" Iron Man 2 movie tie-in line.