Colonel Jonathan "Jack" O'Neill was the commanding officer of SG-1, the flagship unit assigned to the Stargate Command facility. An officer in the United States Air Force, O'Neill was pulled out of retirement and assigned to lead the first Stargate mission to Abydos. He was selected because of his state of depression and self-hatred following the accidental death of his young son, Charlie.
O'Neill was born in Chicago (October 20, 1952, according to his security ID), and raised in Minnesota. He has made many enemies in his years of service, and arguably fewer friends. However, his character has nobility that many of those encountered lack. Beyond the death of Charlie, very little is known about O'Neill's early years. He possess a sharp, sarcastic sense of humor, and is not above taunting an enemy in the heat of battle, or while in captivity.
If you count the skull fractures, Jack has had nine broken bones. He was parachuting between the borders of Iran and Iraq in the 1980s and hit the ground hard. There was no rescue. Instead, he spent nine days making it out on his own, back into allied territory. Jack spent several years in a black-ops unit of the U.S. military, and was imprisoned in Iraq for four months after a mission under the command of Frank Cromwell went bad.
With this in mind, it can be deduced that O'Neill married before 1988. He confirmed he and wife Sarah were together at the time of his imprisonment, since she was his primary motivation for escaping. Sometime after escaping the prison, Charlie O'Neill was conceived.
Close relationships seem to be difficult for Jack. Major Charles Kawalsky was a friend of O'Neill, despite the fact he never knew Jack had a son. Kawalsky claimed he could beat jack at any game of street hockey. They had served together on at least one black ops mission in East Germany, in 1982. Their mission was to infiltrate a wooded compound and capture a Russian agent code-named "Boris"; but enemy soldiers were waiting, and O'Neill's friend and commanding officer, John Michaels, was killed.
During his off hours Jack spent time with his wife and son. Family brought terrific meaning to his life. Simple games of catch and baseball, his son's favorites, fulfilled the parts of his existence that were inaccessible through his military career. But one fateful autumn day, on the day Charlie came home from school with his class pictures, the boy uncovered his father's handgun and fatally shot himself inside their home. Jack and Sarah heard the shot from outside the house, and rushed Charlie to the hospital. The child did not survive.
The impact of Charlie's death sent O'Neill into deep depression. He was deactivated from duty until two of General West's officers arrived at his house, informing him that he had been brought back into active service at the Creek Mountain facility. The top-secret Stargate project was approaching a critical juncture. O'Neill accepted the mission that, if Dr. Daniel Jackson succeeded in opening this "door to heaven," he would go through to the other side to assess the situation and, if he found any hostile threats to Earth, would give his life to destroy the Stargate with a nuclear weapon.
The Stargate was opened around 1996, forever changing O'Neill's life. On the other side of the portal was the Supreme System Lord Ra, who had seeded the world of Abydos with humans. With the help of Jackson and the native Abydonians, O'Neill instead used the bomb to obliterate the false god in orbit aboard his mothership. O'Neill returned to Earth, leaving Jackson, per his request, on Abydos.
Arriving home from the mission, O'Neill found Sarah wished him gone from their home. Soon divorced, he was alone for the first time in over a decade. With the Stargate program shut down and transplanted to Cheyenne Mountain, Jack retired from service. He quit smoking and spent much of his time in solitude, some on his roof staring at the stars through a telescope. It was there on his roof, one year later, that he learned that the Stargate had been reopened and a new threat had emerged.
With the inception of Stargate Command under Major General George Hammond, O'Neill agreed to come out of retirement to command the flagship field unit, SG-1. Along with Samantha Carter, his new second-in-command, he returned to Abydos to retrieve Dr. Jackson and uncover the source of the new Goa'uld threat. But his good friend Skaara, an Abydonian boy, was soon kidnapped by the Goa'uld System Lord Apophis, giving O'Neill a very personal reason to seek out and fight this new enemy.
The SG-1 team and the worlds they have explored have forced O'Neill to reassess his future and his relationships. His initial dislike for Jackson changed to a fondness over the course of many years. Frequently disagreeing with the scientist, he found common ground nonetheless, realizing that both complemented each other's strengths, both in diplomacy and in battle. When Jackson died and ascended to a higher plane of existence, O'Neill struggled with how to deal with his grief -- but was eventually reunited with his lost friend. Jack also became a good friend and brother of Teal'c, a warrior as much as he, whom he convinced to turn against the Goa'uld and join them.
Hammond, despite being his commanding officer, has also become a friend and confidant. Frequently putting up with Jack's jagged-edged and sarcastic attitude, he calms the storms of frustration within the man in any decision he is forced to make. And beyond his friendship forged with Samantha Carter, O'Neill has confessed that he has come to care about her a lot more than their military relationship allows him to. Regulations prevent them from initiating a romantic relationship.
Among his many achievements over the years, O'Neill has been implanted with a symbiote twice, one a Goa'uld and one a Tok'ra named Kanan. He has had the Ancients' library downloaded into his brain twice. He kidnapped an alien child named Merrin to allow her to experience life as a kid. He died and was revived countless times in Baal's sarcophagus. He has spent three months becoming part of Edoran society, believing he was fated to live out his life there. He was framed for the murder of the U.S. senator Robert Kinsey, rapidly aged by Goa'uld nanocites, possessed by a microscopic alien race, trapped in a time loop, and saved Earth more times than he can count.
Many of Jack's dearest friends have not necessarily been human. Thor, the supreme commander of the Asgard fleet (whom Jack knows as his "buddy"), has been a friend from the beginning. The Asgard saw the potential of the human race in Jack and chose to ally themselves with Earth. Thor has even revealed that the Asgard have found the colonel to be quite unique -- the next stage in human evolution.
Having spent seven years in command of the SG-1 team, O'Neill's life has certainly been changed for the better. He was promoted to Brigadier General and replaced Hammond as the commander of the S.G.C. He was never quite comfortable with the desk job, and left the position after one year. He was again promoted, to Major General, and now serves in the higher levels of the program -- at the newly created Homeworld Command office at the Pentagon, in Washington, D.C. Fortunately for Jack, his kind heart and courageous spirit only serve to better relations with his teammates, allies, and the rest of the species he encounters throughout the galaxy.
"Stargate" the Movie - Following the accidental death of his son, Jack O'Neill agrees to lead a military team through the newly-activated Stargate to another planet, where he intends to sacrifice his life to destroy the gate.
Children of the Gods - O'Neill is pulled out of retirement and made commander of SG-1, and fails in his attempt to rescue Skaara and Sha're from the Goa'uld.
The Enemy Within - Jack loses a close friend when Major Charles Kawalsky is infested by a Goa'uld parasite, and dies in the fight against it.
Cold Lazarus - O'Neill learns that an alien entity has created a duplicate of him, which has returned to his ex-wife on Earth to try and heal his "pain." Jack comes face-to-face with the memory of his dead son.
Brief Candle - Infected by Goa'uld nanocites, Jack is condemned to live out the remainder of his brief life on the planet Argos when he begins to rapidly age.
Fire and Water - Jack tries to cope with the tragic death of Daniel Jackson -- but soon comes to realize that it is a false memory placed in his mind.
Solitudes - A malfunction of the Stargate traps O'Neill and Carter on a glacier in Antarctica, and an injured Jack must order Sam to escape with her life and let him die.
There But For the Grace of God - In an alternate reality, General Jack O'Neill sacrifices his life to help Daniel return to our reality with a warning of an impending Goa'uld attack.
Within the Serpent's Grasp - O'Neill finds that Skaara (possessed by the Goa'uld Klorel) is leading an attack ship to Earth, and is forced to shoot and kill him to save Daniel's life.
The Gamekeeper - Captured by an alien virtual reality system, Jack is forced to relive a failed black-ops mission from his past -- over and over again.
Message In a Bottle - An alien organism takes over Jack's body, pinning him to the wall of the gate room with an ancient orb device. The beings are able to communicate with the S.G.C. through the colonel.
The Fifth Race - O'Neill inadvertantly has the entire Ancients' library of knowledge downloaded into his brain. As he slowly loses his faculties, the knowledge drives him to an unexpected meeting with the Asgard in another galaxy.
A Matter of Time - When the S.G.C. gates to a world near a black hole and can't shut off the Stargate, Jack must try and save Earth with help from a former commanding officer with whom he has bad history.
Show and Tell - O'Neill gets to know a young boy sent through the gate by the Re'tu, who wishes to take the name "Charlie," after Jack's late son.
Out of Mind - O'Neill, Carter and Jackson are kidnapped by Hathor, who convinces them that they've been cryogenically frozen for over 70 years.
Into the Fire - Captured by Hathor, O'Neill is infested with a Goa'uld symbiote by Hathor. Thanks to intervention by a Tok'ra operative, the symbiote is killed -- and Jack kills Hathor.
Fair Game - The Asgard request that O'Neill represent Earth when the System Lords arrive for a summit.
Learning Curve - Jack defies orders and takes a young alien girl off the base, in order to expose her to a little of what it means to be a kid.
Point of View - Samantha Carter from an alternate universe arrives at the S.G.C., and Jack must come to terms with the life he never had when he learns that they were married in her world.
The Devil You Know - Held prisoner on Ne'tu by Apophis, Jack is drugged and manipulated by the Goa'uld to see his dead son.
Pretense - Jack and Daniel argue Skaara's case in a Tollan trial to determine whether he or the Goa'uld Klorel has priority over his body. They win, and Skaara is returned to them.
A Hundred Days - A meteor strike traps Jack on another world, where he lives for three months with little hope of returning home -- and falls for a local Edoran woman, Laira.
Shades of Grey - Jack retires from the S.G.C. and is drafted by Maybourne to command a rogue N.I.D. unit off-world, but turns them all in to the U.S. government for stealing from Earth's allies.
Nemesis - Thor transports O'Neill up to his Replicator-infested ship in Earth's orbit, and Jack plans the ship's destruction to save Earth -- though he knows he will not survive.
The Other Side - On the verge of a deal that will give Earth access to all of Euronda's advanced technology, O'Neill turns on their new allies when he finds out that they are genocidal warmongers.
Divide and Conquer - To prove that they are not Goa'uld sleeper assassins, Jack and Sam must confess their personal feelings for each other.
Chain Reaction - When the rogue N.I.D. blackmail General Hammond into retiring, O'Neill risks everything to turn the tables on Senator Kinsey and get Hammond reinstated.
2010 - In an alternate future, a cynical Jack O'Neill helps his friends change the past to avoid Earth's doom.
Entity - An alien entity takes over Carter's body, and Jack must sacrifice her life in order to destroy it.
Enemies - O'Neill is betrayed by Teal'c, who has been brainwashed by Apophis, and must shoot him in order to bring him back to Earth.
Meridian - Jack loses one of his closest friends when Daniel is exposed to a lethal dose of radiation, and ascends to a higher plane of existence. O'Neill makes sure that Kelowna doesn't blame the lab accident on Daniel.
Revelations - Still dealing with the death of Daniel Jackson, O'Neill and SG-1 are called on by the Asgard to rescue Thor and a vital Asgard laboratory from the Goa'uld.
Redemption, Part 2 - Jack saves the world (again) by sending the Stargate through a hyperspace window before it is detonated by Anubis's weapon.
Descent - O'Neill and Carter nearly drown when SG-1 tries to salvage a seemingly abandoned Goa'uld mothership that has arrived in Earth's orbit. The ship is lost, but O'Neill learns to accept Jonas Quinn as a member of SG-1.
Frozen - A mysterious disease leaves Jack on the edge of death, and he agrees to take a Tok'ra symbiote named Kanan to save his life and to allow the Tok'ra to retrieve valuable information from the symbiote.
Abyss - When Kanan leads O'Neill to Baal's secret fortress and is forced to leave him, Jack is captured and tortured by the Goa'uld. An ascended Daniel arrives and offers to help him ascend, but Jack remains convinced that he isn't capable of it.
Smoke and Mirrors - O'Neill is arrested when a video surveillance tape shows that he assassinated Senator Kinsey. SG-1 learns that it was an N.I.D. agent using alien mimic technology to look like the colonel.
Paradise Lost - Misplacing his trust in Maybourne, O'Neill finds himself trapped on an alien moon with him. When Maybourne begins to show signs of madness, Jack is forced to shoot and nearly kill him.
Fallen - Jack is reunited with his old friend when Daniel Jackson descends to his mortal form, and returns to Earth.
Fragile Balance - An Asgard scientist kidnaps O'Neill and replaces him with a teenage clone. Thor arrives to help out, and tells Jack that he represents an evolutionary step forward for human development. (Note: O'Neill's date of birth is given in this episode.)
Evolution, Part 2 - O'Neill decides to go after Jackson and Lee, who have been kidnapped in Honduras -- but must meet up with an old associate, Burke, to make the mission a more probable success.
Lost City, Part 1 - To save Earth and keep the Ancients' repository of knowledge from falling into Anubis's hands, Jack O'Neill downloads the library of the Ancients into his brain -- again.
Lost City, Part 2 - O'Neill finds that he possesses the healing powers of the Ancients, saves Earth from Anubis by discovering an Ancient super-weapon under the ice of Antarctica, and is forced to freeze himself to prevent his inevitable death.
New Order, Part 2 - Jack is saved by Thor, who removes the Ancient knowledge from his head. He is promoted to Brigadier General and made the new head of Stargate Command.
Rising, Part 1 - O'Neill arrives at the Antarctic outpost Atlantus, and gives Dr. Weir's expedition a go to travel to the Pegasus Galaxy.
Zero Hour - Facing squabling alien dignitaries, the capture of SG-1 by the Goa'uld, a plant run amok, and the impending visit of the President, O'Neill considers resigning his desk job. But he decides to stay, and the President endorses his command.
Moebius, Part 1 - O'Neill leads the team 7,000 years into the past to steal a Z.P.M. from Ra in ancient Egypt, but the team finds itself stranded.
Moebius, Part 2 - Daniel reveals that Jack died trying to start an uprising against Ra. But the timeline is averted, and the mission into the past never takes place.
Avalon, Part 1 - O'Neill has left Stargate Command and Colorado Springs, turning over command to General Hank Landry, with whom he has a personal relationship. His new position is still unknown.
Origin - Jack -- now a two-star General -- pays a brief visit to Daniel at the S.G.C.
200 - Jack returns to the S.G.C. to visit when the members of SG-1 are made consultants on Martin Lloyd's "Wormhole X-Treme!" movie.
The Real World - Infected by Replicator nanites, Elizabeth Weir dreams of another life where General O'Neill helps her to recover from a psychotic break.
The Return, Part 1 - When the Ancients return to Atlantis, O'Neill and Richard Woolsey are assigned as liaisons with Earth.
The Return, Part 2 - O'Neill and Woolsey attempt to hide from the Replicators, who have taken control of Atlantis, until Sheppard's team can arrive.
The Shroud - O'Neill confronts his friend Daniel Jackson directly when Jackson is turned into a Prior of the Ori, and must decide whether he can still be trusted.
Stargate: Continuum - After Baal alters the timeline SG-1 encounters Jack O'Neill in the arctic, and is unable to convince him they they are old friends.
Air, Part 1 - O'Neill and Dr. Rush recruit Eli Wallace into the Stargate program, sending him to the Icarus Base in the hopes that he can solve the ninth chevron problem.
Air, Part 3 - O'Neill orders Colonel Everett Young to step up and do what has to be done on the Destiny.
Earth - General O'Neill backs Telford's risky plan to dial Destiny's gate back to Earth.
Subversion - Jack makes his first visit to Destiny via the Ancient communication stones, granting Colonel Young permission to do whatever is necessary to get information out of a traitor.
Incursion, Part 1 - O'Neill communicates with Colonel Carter, on an unsuccessful mission to rescue Dr. Rush and stop the Lucian Alliance from gating to Destiny.