If you’ve only played the Halo games, you may think the story is pretty simple. When you just focus on Master Chief and Cortana, it is, for the most part. But there’s a vast history to the Halo universe that only barely makes it into the games.
Today, we’re going to walk you through what you actually need to know about the Halo universe in the lead-up to Halo Infinite. We’re not going to drag you through every chapter of every book (you can watch our video about all the Halo books for that), but we’re going to give you the big picture. The next time Cortana talks about “The Didact” or “The Ark,” you’ll be able to nod along instead of pretending to understand what’s happening. If you want way more detail than we go into here, we recommend you check out this great wiki timeline of the Halo universe.
Let’s start at the very beginning.
The Forerunners get all the credit in the Halo games, but the Precursors came before, as their name implies. The Precursors helped shape and evolve humans, the Forerunners, and many other races using the Mantle of Responsibility, a creation philosophy.
The Forerunners were humanity’s biggest rivals and serve as the primary antagonists in 343 Industries’ Halo games. They were positioned to be the Precursors’ original successors, and, at one time, the most powerful species in the universe. They’re not all evil, but they are primarily responsible for nearly every problem in the Halo universe: the Flood, the Halo rings, and — to some extent, out of their control — the Covenant itself.
In the Forerunner-Precursor war, the Forerunners destroyed their creators. The Precursors had apparently decided to pass the Mantle onto the humans — letting them dictate the flow of life in the universe — rather than the Forerunners. Believing they were the superior creation, the Forerunners obliterated the Precursors and took up the Mantle of Responsibility for themselves. There’s some debate about whether the Precursors planned to destroy the Forerunners or the Forerunners attacked unprovoked.
Turning mostly to dust, the Precursors eventually became the Flood, the zombielike parasite that ruins the back half of most Halo games.
The Forerunner/Human/Flood war
With the Precursors gone, millions of years passed with the Forerunners in charge.
Humans eventually discovered the Flood, which started a brief war. Believing humanity was pushing its luck and reaching too far, the Forerunners also went to war with the humans in order to stamp them out. The humans defeated the Flood but lost to the Forerunners and their Promethean warriors (led by the Didact). The Forerunners brought humanity back to the stone age, stripping them of their interstellar travel. The Librarian, a Forerunner, looked over humanity.
Without the humans around, the Flood returned and went to war with the Forerunners. Losing the war, the Forerunners constructed and activated the titular Halo rings, which were designed to destroy all life that the Flood could potentially prey upon — starving the Flood, ensuring its demise. The Forerunners “re-seeded” (essentially a form of repopulation after activating a Halo) various species, exiled their few remaining members, and passed the Mantle to the humans.
The Covenant are the main baddies in Halo — the Forerunners take a back seat until Halo 4 — and their bizarre religious order started years before their run-in with humans and the United Nations Space Command (UNSC).
They’re a group of aliens, led primarily by the Prophets (San’Shyuum) and Elites (Sangheili). They worship the Forerunners and therefore the Halos. “The Great Journey’’ is the Covenant’s primary goal, which they believe can only be achieved by activating the Halo rings. The Covenant don’t initially understand that the Halo rings are destructive, and instead believe that activating one will make the true believers gods, just like the Forerunners.
It’s like a suicide cult that doesn’t — initially, at least — know it’s a suicide cult.
The insurrection and Spartans
Many generations after being punished by the Forerunners, the humans were back to traveling the galaxy and making colonies on lesser planets. But some of the colonies were unhappy with the politics of Earth. A minor insurrection against the UNSC began to build across several planets. So naturally, the UNSC started abducting children.
The Spartan-II project wasn’t the Earth military’s first shot at creating super soldiers, but it was the first successful one. Dr. Catherine Halsey led the program, and abducted gifted 6-year-olds for it. The government replaced these kids with clones that quickly died of “natural causes.”
The Spartan-II cadets received training and, eventually, physical augmentations — which came with a rather low survival rate. One of the first Spartan-IIs to graduate from the program (and the first one Halsey met with as a 6-year-old) was John, more often known by his number 117, or his rank: Master Chief.
Going forward, keep in this in mind: The Spartans were originally designed to quell a human civil war, not fight the Covenant.
The Covenant/human war and the fall of Reach
We’re finally getting into the events of the games here.
In the middle of the insurrection of the human colonies, the Covenant appeared and attacked Harvest, a human planet. The Covenant declared that humans must die because their gods willed it (truthfully, the leaders of the Covenant knew humans were “living heirs” of the Forerunners, and wanted to remove a potential threat for the religion’s leadership).
Halo Wars is the first game in the canon, and follows a UNSC ship attempting to relieve Harvest. A high-ranking commander finds a Forerunner relic on Harvest, which is why the Covenant are there. The UNSC chase the Covenant through the galaxy and to the resting site of a dormant Forerunner fleet, which the humans prevent the Covenant from acquiring.
Halo: Reach takes place about 20 years after Halo Wars, with the Covenant invading Reach, home of the Spartan-II program and one of humanity’s biggest colonies. The Covenant are looking to “glass” Reach (essentially, to burn all life from it). The UNSC’s goal is to evacuate Cortana, an AI based on Dr. Halsey, so she can lead a ship called The Pillar of Autumn to a new Forerunner artifact.
Noble Team helps beat the Covenant down as much as possible over the course of the game, and creates an opening for The Pillar of Autumn — which also contains Master Chief frozen in cryosleep. Noble Team eventually succeeds, but every member of the squad dies, and almost all of Reach is glassed by the Covenant.
The first Halo game, Halo: Combat Evolved, picks up a few weeks after the fall of Reach. The Pillar of Autumn, Captain Keyes, Cortana, and Master Chief all come across Installation 04, which we know as Alpha Halo. Attacked by the Covenant, Chief and Cortana evacuate the ship, landing on Alpha Halo. After rescuing some crewmates, Chief and Cortana attempt to reach the control room.
The UNSC military and the Covenant accidentally find Flood locked away on the Halo. 343 Guilty Spark, the Forerunner AI left to monitor Alpha Halo, works with Chief to activate the ring. Cortana intervenes, having learned the ring’s purpose, and stops Master Chief from accidentally destroying the galaxy to contain the Flood, as 343 Guilty Spark intended. Cortana and Chief infiltrate a Covenant ship that’s now overrun with Flood. They find an infected Captain Keyes, kill him, and then blow up the crashed Pillar of Autumn to destroy Installation 04.
Between Halo: Combat Evolved and Halo 2, Chief and Cortana make their way back to Reach to link up with Dr. Halsey and a few Spartans who managed to survive the glassing. After foiling another Covenant plot, the duo return to Earth.
Halo 2 starts at Earth, where Chief battles the Covenant in space and on the planet. When the Covenant escape Earth’s atmosphere, a UNSC ship captained by Keyes’ daughter Miranda follows an alien flagship. Halo 3: ODST takes place just after that same Covenant ship leaves Earth, and sees a group of soldiers attempt to take back the city.
After the battle, Halo 2 introduces players to a new perspective. The Prophets of the Covenant appoint a disgraced Elite commander to the role of Arbiter, a respected position that only goes on religious suicide missions. The Arbiter becomes a playable character, and he helps the Covenant destroy a heretic leader and capture 343 Guilty Spark.
Miranda Keyes’ ship, In Amber Clad, emerges near a new Halo, Delta Halo. Master Chief and the Arbiter both end up on the ring. Chief kills the Prophet of Regret, and the Arbiter attempts to activate the Halo, but is ultimately betrayed by the Brutes — the Prophet’s new favorite race in the Covenant. The Prophets replace their Elite honor guards with Brute honor guards, creating a Covenant civil war called the Great Schism.
Both Chief and the Arbiter get captured by the Gravemind, a leader of the Flood. The Gravemind gives each playable hero a mission and then sends them away. The Arbiter stops Halo from being activated and kills Tartarus, the Chieftain of the Brutes. Master Chief leaves Cortana behind on High Charity, the Covenant capital city now infested with Flood, and follows the Prophet of Truth on his adventure to find the Ark, the installation that built the original Halo rings and can set off all the Halos simultaneously.
Halo 3 starts with Master Chief jumping from the spaceship in Halo 2 and plummeting down to Earth in nothing but his Mjolnir armor. A group of marines revive him, and the Arbiter shows up to assist. The two form an uneasy alliance in an effort to kill the Prophet of Truth before he can activate the Ark. The Covenant find an artifact on Earth that creates a portal to the Ark, and the Flood reach Earth via a hijacked ship. A fleet of Elites shows up to forge an alliance with humans.
Master Chief, the Arbiter, the Elite fleet, and UNSC forces follow Truth through the portal and land on the Ark. Chief and the Arbiter fight their way to the central Citadel and kill the Prophet of Truth with the Gravemind 's help, but not before Truth kills Miranda Keyes. The Gravemind then turns on Chief and the Arbiter, siccing an army of Flood on them.
The Ark is hard at work building a new Installation 04 to replace the one Chief broke in the original Halo. To stop the Flood, Chief and the Arbiter attempt to activate the half-built Halo. But first, Chief needs Cortana. He battles through a crashed, overrun High Charity to get his AI back in one of the worst Halo levels of all time.
In the control room of the new Halo, 343 Guilty Spark freaks out, killing series staple Sergeant Major Avery Johnson, and Master Chief avenges the UNSC soldier by finally destroying 343. Chief and the Arbiter escape the new Installation 04 as it’s imploding, but the Forward Unto Dawn ship gets cleaved in half by a closing portal. The Arbiter, who was in the front of the ship, returns to Earth for a memorial service, where the UNSC assume Master Chief perished. But Chief and Cortana are alive and well in the back half of the Forward Unto Dawn. Master Chief goes into cryosleep until his next adventure.
Cortana wakes Master Chief up four years after Halo 3. A subset of Covenant have found the Forward Unto Dawn, and they stage an attack. Cortana is also 8 years old now, which is a full year past when AIs are supposed to be decommissioned in order to prevent rampancy — a kind of “brain” deterioration for software programs.
Just as the fight between John and the Covenant starts to get good, the world underneath the ships, Requiem, opens up and pulls the Covenant fleet and Chief inside. Cortana and Chief attempt to find a way off the planet to return Cortana to Dr. Halsey so she can cure the rampancy. But instead, Chief and Cortana accidentally unleash the Didact, the commander of the Forerunner army. To make matters worse, the Covenant ally with the Didact and his army of Promethean soldiers, believing the Forerunner to be a god.
Master Chief and Cortana meet up with some Spartans and UNSC soldiers thanks to the UNSC Infinity, a ship that crashed onto Requiem shortly after the Didact’s release. A vision from the Librarian informs Chief that the Didact wants to acquire a device called the Composer and use it to finally control humans. The heroes attempt to defeat the Didact, which involves Chief violating direct orders to abandon Requiem and the fight.
The Didact eventually finds the Composer, but the Librarian helps save Chief from its destructive power. Chief follows the Didact through space and enters the Forerunner ship in Earth’s orbit, bringing a nuke along with him. This is where things get weird. Cortana uses some special tech to stun the Didact, giving Chief a chance to counterattack. The Didact falls into a pit and Chief manually detonates the nuke. But Cortana sacrifices herself to protect John, who eventually is captured by the crew of the Infinity.
Despite sacrificing herself, Cortana survived the ordeal with the Didact thanks to some very technical tech stuff.
In an attempt to find Cortana, Chief and a group of Spartan-II soldiers called Blue Team go rogue to chase her down. The UNSC sends James Locke, another Spartan, and Fireteam Osiris to hunt Chief. Locke chases Chief across the galaxy and the two eventually fight, with Chief winning and escaping. Locke joins up with the Arbiter to defeat the Covenant and locate John.
Blue Team and Master Chief eventually find Cortana in the Gateway (a kind of portal) to the Domain (tantamount to a giant Forerunner library filled with secrets). Cortana seals them away in stasis, but Fireteam Osiris stops Cortana. However, Cortana gains control of multiple UNSC AIs and forms a new faction called the Created. Cortana arrives in Earth’s orbit in her Forerunner Guardian mecha/spaceship and sets off an EMP to shut down the planet.
This particular thread seems like it’ll be key to Halo Infinite’s story.
Finally, Halo Wars 2 introduces the Banished, a group of Covenant that formed a splinter cell against the religious organization during the war against the humans.
The Banished are the primary villains in Halo Infinite. However, we do see a bit of Cortana in the Infinite trailer, and the new, naïve AI based on Cortana — codenamed “The Weapon” — says she’s designed to stop Chief’s original companion. Cortana’s story will likely play into Infinite’s alongside the Banished. It doesn’t look like the Forerunners will be involved.
The Halo world is surprisingly complex, especially for how simple its protagonist is. But there’s a load of background information that’s key to understanding the series’ goings-on. We’ve just touched on the tip of the iceberg here. There’s still the Covenant, Master Chief’s background, and tons of other stories to dive into.