Halo 5 is almost here, and if your knowledge of series is lagging, Xbox UK's Acey Bongos has prepared a series of quick-hit story primers for the first four Halo games.

We've compiled Acey's videos into a single location for your perusal and provided some commentary in case you're unable to watch. Naturally, this article contains spoilers.

Halo: Combat Evolved

Halo: CE begins on the military spaceship the Pillar of Autumn, which is under siege from a fanatic alliance of alien races, known as the Covenant. As the Pillar of Autumn and its crew exited slip-space travel during their retreat, they stumbled upon a gigantic ring-shaped artificial world, an eponymous Halo.

The Covenant and the surviving human military, formed of the super-human Spartan known as the Master Chief and the UNSC, battle all the way onto Halo's surface. While there, the UNSC A.I. known as Cortana discovers that Halo is an ancient galaxy-threatening weapon of mass destruction, created by the Forerunners. It's designed to prevent the spread of a dangerous parasitic life-form, known as the Flood, which the UNSC unwittingly unleash during their time on the Halo ring.

The Chief and Cortana decide to destroy Halo by causing the self-destruction of the Pillar of Autumn, which crash landed on the ring during the initial battle. They succeed in their mission, but the Chief remarks at the end that they're just getting started.

Halo 2

Halo 2 begins with the public trial of Thel'Vadam; a Covenant Elite blamed for failing to prevent the destruction of the Halo ring. The Covenant worships the Forerunner technology and believes that activating the galaxy-destroying Halo weapon will send them on the "great journey" into a transcendent, Heaven-like paradise.

Meanwhile, Covenant forces invade Earth itself, attacking the Kenyan city of New Mombasa. After the UNSC and Master Chief beat the Covenant back, the Prophet of Regret flees with the remainder of his forces into slip space - the Chief tails in hot pursuit. As they exit slip space, the Chief and Cortana happen upon yet another Halo ring, realizing that there are more than one.

While these events are taking place, Thel'Vadam is taken to the Covenant leaders, who offer him a chance at redemption. Thel'Vadam becomes The Arbiter, a direct servant of the Covenant hierarchs. He's sent to assassinate a Covenant heretic, and while there, he discovers 343 Guilty Spark, an A.I. designed to oversee the Halo rings. Guilty Spark and the Arbiter return to the ship known as High Charity, which has just received a distress call from the Prophet of Regret on the new Halo ring.

High Charity arrives too late to prevent Regret being beaten to death by the Master Chief. The Covenant respond by bombarding the area, sending the Chief plummeting into a gigantic artificial lake - where he is pulled further into the depths by a gigantic tentacled creature.

Disturbed by the death of Regret, the remaining Prophets appoint a new race to be their guardians - the Brutes - who are subsequently ordered to kill the Arbiter and his Elite brethren. The Arbiter is thrown from High Charity, only to get captured by the same creature that ensnared the Master Chief.

The beast turns out to be the Gravemind, a gargantuan beast that commands the parasitic Flood. The Gravemind informs the Arbiter what the Chief already knows - that the Covenant's desire to activate the Halo rings would destroy all three of their species. They form a reluctant alliance, and resolve to prevent the activation of Halo. During the ensuing battles, the Arbiter succeeds in preventing the second Halo ring from firing, but in doing so, he activates a failsafe that allows the remaining rings to be activated from a remote location, known as the Ark. The Prophet of Truth heads directly to Earth, having learned from 343 Guilty Spark that an artifact there will take them directly to the Ark. Thankfully, the Chief is again on the scene, promising to the end the fight as the credits roll.

Halo 3

The Chief, Sergeant Major Johnson and the Arbiter rendezvous in Africa, intent on stopping the High Prophet of Truth from finding the path to the Ark. Following an intense battle, the UNSC forces fail to prevent Truth from activating the artifact, which then creates a slip space portal leading directly to the Ark. As the Chief and his allies regroup, a Flood-infested ship crash-lands nearby. On the ship, the Chief discovers a message left by Cortana, who remained on the Covenant ship High Charity behind during the events in Halo 2.

With new information, the Chief and his allies follow Truth through the portal, discovering a gigantic installation designed to trigger the Halo rings remotely. Aided by the Gravemind and the Flood, the Chief and the Arbiter defeat the Prophet of Truth and prevent the activation of Halo. With the threat of destruction removed, the Gravemind turns on the Chief, intending to infect the galaxy unabated.

The Chief and his allies discover that the Ark is automatically constructing a new Halo ring, to replace the one destroyed in Halo: CE. Guilty Spark reveals that activating this ring would destroy not only the premature Halo but also the Ark itself, preventing the activation of other Halo rings. The Chief decides to activate the ring, knowing that it would destroy the Flood infection that has taken hold on both the Ark and the new ring. Naturally, Guilty Spark protests, as the new ring is his ring, rebuilt from Halo: CE. Guilty Spark attacks the Chief, only to get defeated. The Chief activates the new ring, causing a gigantic explosion that leaves him and Cortana, stranded in deep space on the wreckage of the ship Forward Unto Dawn.

Halo 4

Having drifted in cryonic sleep for four years, Cortana wakes Master Chief noting that enemies have boarded the wreckage of the Forward Unto Dawn. The remaining Covenant fanatics have arrived hunting a planet known as Requiem, a world once used by the Forerunners - the creators of the Halo rings. Eventually, the Forward Unto Dawn is caught in Requiem's gravity well, and the Chief and Cortana crash land on the planet.

While there, Cortana appears to malfunction, revealing that she's suffering from rampancy, a terminal illness that's caused by a flaw in the UNSC's model for A.I. development. Having formed a close relationship, the Chief promises to bring Cortana to her creator, Dr. Halsey, with the hope that she can fix Cortana.

Eventually, the UNSC ship Infinity answers the Forward Unto Dawn's distress call. Cortana calls on the Chief to disable Requiem's communication jamming so they can warn the Infinity about Requiem's gravity well. Unfortunately, they unleash the Didact in the process, an ancient and advanced Forerunner warrior imprisoned on the planet. Thinking him a God, the Covenant join forces with the Didact and his mechanized Promethean warriors.

In the ensuing battle, the Chief is contacted by the Librarian, another Forerunner, who imprisoned the Didact originally. She reveals that the Forerunners failed to find a comprehensive way to combat the Flood, instead opting to turn their soldiers into mechanical versions of themselves using a device called the Composer. The Didact was imprisoned for forcing ancient humans - who were being overseen by the Librarian - to be "composed" against their will. The Chief is granted immunity to the Composer and resolves to defeat the Didact.

The UNSC Infinity orders the Chief to retreat with them to Earth and hand over the deteriorating Cortana. The Chief refuses, instead opting to prevent the Didact from recovering the Composer, which is housed on a secret research facility studying one of the remaining Halo rings. The Chief and Cortana fail to prevent the Didact's recovery of the Composer, which is used to turn the research facility's inhabitants into digitized slaves.

Chasing the Didact to Earth, the Chief, aided by Infinity, manages to board the Didact's ship with a nuclear weapon while Cortana infects its computer systems. The Didact begins blasting the Composer at Earth, digitizing the inhabitants. The Chief, aided by Cortana within the ship's computer, overwhelm the Didact, sending him into a slip space corridor. Master Chief then detonates the nuke with his bare hands, destroying the Composer. Cortana uses the ship's systems to save Master Chief from the ensuing explosion, giving her life in the process.

The Chief is discovered by the UNSC floating amidst the wreckage. Back on board the Infinity, the Chief laments Cortana's death and appears to fall into disillusionment, setting the tone for Halo 5.

Halo 5

Halo 5 begins with the reported "death" of the Master Chief, as ONI, the Office of Naval Intelligence, begins spreading propaganda to cover up the truth. They believe the Master Chief has gone rogue, taking his Blue Team with him, and become paranoid about what he's planning.

ONI enlist Spartan Locke and Team Osiris to hunt down and eliminate the Chief, as a new enemy emerges, threatening the entire galaxy.

Subscribe to Xbox UK's YouTube channel for more official Xbox content

Of course, the best option is to pick up Halo's Master Chief Collection and see it all for yourself. If you're all set, though, know that we're planning a ton of Halo 5 content in the coming weeks. Check in soon for some hands-on impressions with the first few campaign missions (spoiler-free, of course). As a sneak peek - I don't think there's going to be a single disappointed Halo fan come October 27th.

Pre-order Halo 5: Guardians for the Xbox One at Amazon for $59.99 Pre-order Halo 5: Guardians Limited Edition for the Xbox One at Amazon for $99.99 Pre-order Halo 5: Guardians Limited Collector's Edition for the Xbox One at Amazon for $249.99