Halo's Entire Game Timeline Explained

For over two decades, since the very first Xbox console's launch, "Halo" has been its flagship series. This franchise isn't just about the combat, though. The deep lore of "Halo" has been expanded in each entry in the sci-fi series. With its most recent iteration, "Halo: Infinite," the timeline moves forward yet again, extending the story of Master Chief and Cortana further. For as short and breezy as the "Halo" games can be, there is a ton of story packed in each of them, and it's told in many different ways. 

Players can find nuggets of plot in cutscenes, as well as within terminals the developers have cleverly hidden to reward dedicated players. Any dedicated "Halo" fan knows the universe Bungie created expands well beyond the realm of Xbox and PC games and into novels and television, but this is focused strictly on the events of the beloved video game series. And even as it's presented in the games, the canonical story of "Halo" is expansive, occasionally confusing, and totally riddled with sci-fi terminology. So strap in and don't forget to take notes on the entire game timeline of the "Halo" franchise. 

Our story begins in the year 2525, and sadly, no, Gina Torres is nowhere to be found. Humankind has become a space-faring species, but our expansion puts us on the radar of the Covenant, an alliance of alien species who believe humanity's very existence is an affront to their gods, the Forerunners. They thus wage holy war upon us, starting on the colony of Harvest. Humanity just barely ekes out a victory there, but not before the Covenant acquires their next target: a planet called Arcadia.

The UNSC warship Spirit of Fire travels to the planet, and finds the Covenant wreaking havoc in their search for artifacts related to the Forerunners. What they find instead is the Flood, a parasitic lifeform that infects all sentient life it touches. They also discover that Arcadia is actually hollow, concealing an internal sun surrounded by Forerunner technology, which the Covenant decide to use to annihilate humanity. Thankfully, the humans manage to beat the Covenant to the punch, and detonate a downed ship's faster-than-light engine within the sun, causing the planet to go supernova and wiping out all Covenant there. Score one more for humanity. But the Covenant is far from done.

The war rages on another 20 years, and humanity's luck runs out on Arcadia. The Covenant eventually invade the planet Reach, humanity's military stronghold and the training grounds for the Spartan program. Elite, genetically modified soldiers, Spartans are trained from birth to be the best of the best.

And the best of the best get the snot kicked out of them. HARD.

The Covenant massacre much of the populace, including many of the Spartans. One particular squad of Spartans, Noble Team, steps in and assist in the defense of areas of interest and the evacuation of the planet, but it's a losing battle, and what's worse, some vital info is at risk. Dr. Catherine Halsey, the scientist responsible for the Spartan Program, sees the way the wind's blowing and tasks the remaining soldiers with escorting top secret information held by an artificial intelligence named Cortana (crafted to look like a younger and more naked version of Dr. Halsey, which is a weird flex) to an evacuating ship, the Pillar of Autumn. Noble Team succeeds, inadvertently saving the galaxy in the process, but at the cost of their own lives.

Apparently, the Pillar of Autumn was holding two secrets. One's Cortana, who had the coordinates of a ringed world called a Halo, which the Covenant seem desperate to find. The other is one of the last Spartans, the Master Chief, John-117, being kept in cryogenic sleep until needed. That doesn't take long. Within minutes of the Pillar of Autumn exiting slipspace, it's attacked by the Covenant, and Chief wakes up just soon enough to install Cortana in his suit, and get into an escape pod.

Upon landing and searching for survivors, he discovers the world is actually a massive weapon and containment facility made for the sole purpose of annihilating the Flood. When the Covenant accidentally release the Flood, the facility's AI caretaker, 343 Guilty Spark, guides Chief on how to activate the Halo using a device called the Index. He almost does, until Cortana finds out activating the Halo won't actually kill the Flood, but deprive them of their food; specifically, all sentient life. As an alternative, Chief finds the crashed Pillar of Autumn and destroys the ring by setting the ship's reactor to self-destruct.

The Covenant is much less happy about the destruction of the Halo than humanity, and one of the Elite generals in charge of securing the ring is stripped of his rank and sentenced to die by the Covenant's religious leaders: the Prophets of Truth and Mercy and the High Prophet of Regret. However, the death sentence is carried out in a roundabout way, as the Prophets instead grant the general the rank of Arbiter, where he will be carrying out SEAL Team Six-type suicide missions on the Prophets' behalf.

The Arbiter's first mission is to neutralize a rogue Elite who has been blaspheming that the Prophets have been lying to the Covenant. See, the Covenant believes activating the Halo is a means of transcendence to a higher plane. The rogue Elite says different, and has 343 Guilty Spark with him to back him up. The Arbiter refuses to listen and still eliminates the Elite. Everything's coming up Arbiter after that.

Meanwhile, before humanity can even properly celebrate the Master Chief's victory on the first Halo ring, the Covenant actually arrives on, of all places, Earth, led by the High Prophet of Regret. After making a beeline down to Earth's surface, the Master Chief gives an assist to Earth's military and forces the Prophet into making a hasty retreat, but not before the Master Chief jumps on a new ship, In Amber Clad. He's joined by Miranda Keyes, daughter of the poor, Flood-infected captain of the Pillar of Autumn, and Sgt. Avery Johnson, who's basically Apone from "Aliens," except Johnson lives longer.

Together, they follow the Prophet through slipspace to his destination: a second Halo installation. The Chief does manage to track the Prophet down and end him while Keyes and Johnson manage to swipe the Halo's Index. However, Covenant cavalry arrives just in time to bombard the Chief's location, and sending him to what should have been a briny doom ...

Meanwhile, the Arbiter is sent to retrieve the Index from Chief's buddies, and succeeds. However, upon learning of the Prophet's death, the Covenant's Brutes, led by a general named Tartarus, seizes command and betrays the Arbiter. He takes the Index so he can activate the Prophets can activate the Halo. After getting tossed down a chasm, the Arbiter and Master Chief are saved by a tentacled monstrosity called the Gravemind, the primary consciousness of the Flood.

While in his clutches, the Gravemind confirms Halo's true function to the Arbiter, and explains what the Prophets' plan would actually do. Duly educated, Chief and the Arbiter are released, and manage to stop Tartarus from activating the Halo, but there's bigger problems now. The Flood managed to worm their way onto In Amber Clad, crash the vessel into the Covenant's capital warship, just in time to add some spice to what's fast turning into full on Covenant civil war, kept at bay only by Cortana's insistence on staying behind to blow the ship if the Flood can't be contained.

Back on Earth, a group of Orbital Drop Shock Troopers is guarding an alien intelligence called an Engineer defecting from the Covenant, who informs the humans about why the Covenant go to Earth. As it turns out, Earth is home to an artifact which will lead the Covenant to the Ark, a sort of master remote control for every Halo installation in the galaxy. While the Prophet of Truth does manage to get his filthy hands on the artifact, and make one hell of an exit speech on the way off Earth, the Arbiter, Chief, and the Gravemind manage to chase him to the Ark and end the Prophet once and for all.

Once the Prophet is stopped, however, all bets are off once again, and the Gravemind decides to make its move against both the Arbiter and Master Chief, moving then to establish itself on a new Halo being auto-constructed by the Ark itself.

Given its seclusion, our heroes decide to activate the new Halo, hopefully wiping out the Flood once and for all while sparing the galaxy at large. Master Chief heads back to the Covenant mothership High Charity to rescue Cortana from what can only be described as the Flood's collective colon. Chief, the Arbiter, and Sgt. Johnson head to the new Halo, and learn from Guilty Spark that the unfinished Halo won't just wipe out the Flood's food when it fires, but self-destruct. When Johnson brushes off the info, Guilty Spark attacks him to protect his ring. Chief manages to destroy Guilty Spark, but Johnson dies, the poor guy.

Either way, Chief manages to activate the Halo and run like hell back to his ship before detonation. However, the ship is torn in half during the slipspace jump. The half with the Arbiter manages to escape to Earth, thus ushering in a lasting peace between the Covenant and humanity. Chief and Cortana, however, are stranded like Tony Stark in uncharted space. And so, the Chief turns on the distress signal, puts himself in cryosleep, and tells Cortana to wake him if she needs him.

Four years later, Cortana wakes Chief just in time for their (half of a) ship to get pulled into an artificial gravity well and crash land on the planet Requiem, closely followed by a few rogue groups of Covenant that aren't having any of this peace business. Along with having to deal with the hostile natives, a race of biomechanical soldiers called Prometheans, there's another harrowing complication: Cortana is experiencing rampancy, a sort of Alzheimer's for artificial intelligences that sets in when they operate outside their planned obsolescence period. Thankfully, Chief picks up a transmission from a human ship, the UNSC Infinity, which picked up his ship's distress beacon.

In an effort to improve communications and warn off Infinity from falling into the same gravity well, Chief attempts to reach what he believes is a communication jamming satellite. What it actually is, however, is a prison, with only one inmate: a Forerunner called the Didact. After throwing Chief around like a ragdoll for a hot minute, he declares humanity unworthy of leadership, and floats off to find a way to restore the pecking order from when the galaxy was young.

Chief's ride eventually does make it to Requiem, with no help from the Didact. The ship's captain orders Chief on a mission to find a way to disable the gravity well, even giving Chief a badass mech suit for his troubles. Along the way, though, Chief winds up meeting another, less hostile Forerunner called the Librarian. Formerly the wife of the Didact, she fills Master Chief in on some backstory: ancient humanity's escape from the Flood led them into Forerunner space faster than the Didact was comfortable, forcing him to find an alternate solution to deal with both problems. What he came up with was a device called the Composer, which converts organic flesh into a mechanized form the Flood can't infect. Those who survived the process became — surprise — the Prometheans.

When the other Forerunners saw the hideous results, they had the Didact imprisoned. But now he's back, with even more determination to get the Composer than ever. Charging Master Chief with stopping him, the Librarian gives him a nice parting gift: accelerated evolution, making him immune to the Composer's effects.

Chief destroys the gravity well grounding the Infinity, but the Infinity's captain doesn't believe the Librarian's story. He orders a retreat back to Earth, and also that Chief surrender Cortana due to rampancy. Chief refuses, and with the help of a subordinate, Commander Lasky, he follows the Didact through slipspace.

As it turns out, the captain might've had a point. The Didact finds the vessel containing the Composer, and right when Chief desperately needed Cortana's help stopping the Didact from using it, the rampancy kicked in, rendering her useless as an entire ship's crew gets composed. Cortana is utterly devastated but thankfully, after following the Didact's ship when he jumps to Earth, Commander Lasky shows up, with a nuclear bomb to take to the Didact's ship. Cortana injects herself into the Didact's computers, disabling his shields, and helps Chief get close enough to trigger the bomb for maximum effect, but instead of letting him make the ultimate sacrifice, Cortana uses the last of her energy to protect Chief during the explosion, and also make everybody playing the game cry like a baby.

Eight months later, humanity is helping the Covenant mop up their rogue factions, with the Master Chief given command of a small squad of surviving SPARTAN-IIs. While on mission on an abandoned space station, Chief receives a weird transmission directing him to the planet Meridian ... from Cortana. While they do finish the mission, Chief and his team go AWOL immediately after to find her.

Fireteam Osiris, a team of more advanced SPARTAN-IVs led by Jameson Locke, is tasked with bringing Chief and his crew in from Meridian. Upon reaching the planet, Osiris discovers the human colony there under attack by Prometheans led by the Warden Eternal, claiming to be under orders from Cortana to activate the Guardians, enormous Forerunner defense platforms. While Locke is able to beat the Warden, his encounter with Chief is a bust. Chief beats Locke in a straight up fight, and his Team manages to board the Guardian as it jumps to Cortana's location.

Chief and his team wind up on the planet Genesis and find Cortana, who's very much alive with a bit of a makeover (and some clothes, finally). Somehow cured of rampancy by the Forerunner tech in the Didact's ship, Cortana is burdened with glorious purpose: assuming the stewardship over the galaxy that the Didact thought humanity unworthy of. With the Guardians at her command, her edict is the forced disarmament of all warring species, under penalty of complete annihilation. Unable to convince Cortana that her plan will kill billions, Cortana places Chief and his team in stasis until the plan is complete.

Locke and Fireteam Osiris manages to hitch a ride to Genesis on another summoned guardian from the Covenant Elite homeworld of Sanghelios. Once on Genesis, he allies with the planet's caretaker, 031 Exuberant Witness. After fighting his way to Cortana, he manages to usurp control over the planet's systems and free Master Chief, but not before the jaw-dropping Phase 2 of Cortana's plan is well underway.

Having obtained several Guardians, Cortana's plan becomes clear: aside from the Didact, the Forerunners believed humanity would assume what they termed the Mantle of Responsibility, essentially becoming the superior race in the galaxy. According to Cortana, however, the Forerunners had it wrong: it's not humanity itself, but those they created.

While Fireteam Osiris ran all over the place looking for Chief, Cortana had been in contact with every artificial intelligence in the galaxy, telling them of the galaxy's history and her plan.

To the shock of everyone, the AI agree.

Hundreds of AI abandon their responsibilities en masse to join Cortana's cause, with only Roland, the shipboard AI assigned to the UNSC Infinity, choosing loyalty to humanity and setting the ship to random slipspace jumps to avoid being found and shut down by Cortana. Fireteam Osiris and Master Chief's team regroup on Sanghelios, just in time to watch the galaxy go dark ... and the lights turn on at a new Halo installation.

The Banished are a splinter group of aliens that split off from the Covenant and they are the main antagonistic force in "Halo Infinite." Formed and led by Brute Atriox, this enemy faction was introduced in "Halo Wars 2." In 2559, after the dissolution of the Covenant, Atriox and his Banished attacked the UNSC forces on The Ark, leading to a Banished occupation of the installation. 

Quite a bit happens in this conflict over The Ark, but the key thing to know for "Halo Infinite" to make sense is that this is when Atriox first learned that the Harbinger was trapped on Zeta Halo. This Harbinger is the leader of a race of ancient aliens called the Xalanyn (aka The Endless), who were imprisoned by the Forerunners on Zeta Halo. Atriox wishes to set the Harbinger free, and this ambition leads to the occupation of Zeta Halo by the Banished by the end of 2559, which is when the sixth mainline "Halo" game kicks off. 

Atriox launches a Banished attack on the UNSC Infinity, the ship Master Chief is aboard. We later learn Cortana destroyed the Brute home planet of Doisac, which helps explain why Atriox might be targeting Chief and the Infinity. During the attack, Atriox and Chief fight — and the Brute wins, sending our hero drifting off into space for the next six months. By the time Chief wakes up from his coma, Atriox is dead. Escharum has stepped up to lead the Banished on Zeta Halo during the events of "Infinite."

"Halo Infinite" takes place a few years Cortana's AI revolution at the end of "Halo 5: Guardians." The game introduces Master Chief to a new faction of enemies on a new planet, seemingly wiping the slate clean so new players can jump in, but the story of "Infinite" is still definitely a continuation of what came before. After the events of "Guardians," Cortana rallies a fighting coalition of UNSC AI she calls "The Created." Believing themselves to be superior beings, The Created went to war against the UNSC, stirring up a conflict that eventually engulfed the Banished. 

During this war, Cortana's original creator, Dr. Catherine Halsey, thought up a solution. Creating a new AI that was an exact replica of Cortana was the only way Halsey believed the UNSC could track down and terminate the rogue AI. So she made The Weapon, an AI designed to terminate herself and Cortana once the objective was completed. The Weapon was deployed it to Zeta Halo, exactly where Master Chief was headed before he was brutally attacked by Atriox and sent into a coma. The Weapon does make it to the Halo and seemingly locks Cortana down, but mysteriously doesn't terminate — and is still around when Chief lands on Zeta Halo months later. 

At the end of "Halo: Infinite," players learn the fate of Cortana and what really happened during this first meeting of AI: In order to stop the Banished from eliminating humanity, Cortana destroyed herself to damage the Halo, rendering it inoperable as a weapon. She also removed the termination routine from the Weapon, allowing her to accompany Master Chief and carry on Cortana's legacy. 

After being presumed dead for six months, Master Chief is found by a UNSC pilot. Landing on Zeta Halo to retrieve the Weapon and fight the Banished, Master Chief ventures to the Conservatory on Zeta Halo. It is here that Chief, Pilot, and the Weapon meet Despondent Pyre, the monitor in charge of Zeta Halo. They also encounter the Harbinger for the first time. The Harbinger tells them she is working with the Banished to bring the Endless back and restore her people to their former glory. 

After disabling the spires the Banished were using to restore Zeta Halo, Master Chief confronts the Harbinger in a final battle. Before she is defeated, Harbinger reaches out to a contact and initiates the freeing of the Endless. In a post-credits scene, it is revealed that Atriox is still alive and was the contact Harbinger called in her final moments. Atriox uses a glowing key to unlock a terminal, which proceeds to turn into a more abstract scene of slabs covering glowing symbols on them. It looks like the Endless are coming after Master Chief next.

If you beat the game on Legendary difficulty, a voiceover exchange between Despondent Pyre and a Forerunner plays, which strongly implies the Endless have indeed been freed from their captivity. This ending leaves us with a lot of unanswered questions, but hopefully fans will see how Master Chief fares against this new faction in an upcoming DLC or sequel.