Halo Reach takes place in the year 2552, where humanity is locked in a war with the Covenant on the human colony of Reach weeks prior to the events of Halo Combat Evolved. Players control Noble 6, a member of an elite squad of super soldiers, during the battle for the world of Reach. As the Covenant begin their assault on the planet, the UNSC begin their heroic yet ultimately futile effort to halt the brutal alien invaders.
Halo Reach grossed US$200 million on its launch day, setting a new record for the franchise. The game sold well in most territories, moving more than 3 million units its first month in North America. Reviews of the game were positive.
The game begins with the player’s character, Noble 6, joining Noble Team as a replacement for a fallen comrade. Colonel Holland, the team’s commander, sends the Spartans to discover why a relay station on Reach went offline, suspecting damage done by insurgents. Instead of human rebels, Noble Team discovers the Covenant. Soon after, Noble team is deployed to “Sword Base”, an installation belonging to the Office of Naval Intelligence, for defensive purposes; the scientist Catherine Halsey, mastermind of the SPARTAN-II program and the MJOLNIR powered armor worn by SPARTANs, informs Noble Team that the Covenant at the relay were searching for important information.
As the Covenant arrive on the planet en masse, Noble Team is dispatched on various defensive missions such as assaulting a Covenant ground base and removing fortified Covenant defenses. When a massive super-carrier joins the fight, Jorge and Six infiltrate a smaller ship, intending to dock it with the super-carrier then destroy it with a makeshift bomb. When the detonator malfunctions, Jorge sacrifices himself to destroy the carrier; soon after a larger Covenant fleet arrives to continue the assault. Noble Six regroups with the rest of the team in assisting with the evacuation of the planet, during which Kat is killed by a sniper.
Recalling Noble Team to Sword Base, Halsey shows them an ancient Forerunner artifact that she believes is key to winning the war. Noble Six, Carter, and Emile are entrusted with taking the artificial intelligence Cortana, and the information she carries, to the UNSC ship Pillar of Autumn, while Jun is assigned to evacuate Halsey in a Pelican dropship.
En route to the Autumn’s dry dock, Carter became seriously wounded and decides to sacrifice himself and the team’s Pelican to destroy a SCARAB, allowing Noble 6 and Emile to reach the shipyard where the Autumn is located. Emile takes control of a coilgun emplacement to defend the Autumn and Six fights through covenant forces to get Cortana to Captain Jacob Keyes. Emile is slain by Elites, and Six remains on Reach and takes Emile’s place at the gun while the Autumn escapes. The game depicts the opening scene of Halo: Combat Evolved, in which Cortana and the Pillar of Autumn discover the franchise’s titular Halo ringworld, followed by the credits and a personal message of thanks from Bungie.
The post-credits scene puts the player in control of Noble Six’s last stand against overwhelming Covenant forces. Six’s shattered helmet is left discarded on the ground in a shot that mirrors the game’s opening scene. Over thirty years later, the same helmet rests on the grassy plains of a now-rejuvenated Reach. A narration by Halsey eulogizes Noble Team’s sacrifice, which enabled the victory over the Covenant.