Halo 2 is a 2004 first-person shooter game developed by Bungie and published by Microsoft Game Studios. Released for the Xbox, the game is the second installment in the Halo franchise and the sequel to 2001's critically acclaimed Halo: Combat Evolved. The game features a new game engine, added weapons and vehicles, and new multiplayer maps. The game shipped with global multiplayer matchmaking via Microsoft's Xbox Live service. In Halo 2's campaign story, the player assumes the roles of either the human Master Chief or the alien Arbiter in a 26th-century conflict between the human United Nations Space Command, the genocidal Covenant, and the parasitic Flood.
After the success of Combat Evolved, a sequel was expected and highly anticipated. Bungie found inspiration in plot points and gameplay elements that had been left out of their first game, including online multiplayer. A troubled development and time constraints forced cuts to the scope of the game, including the wholesale removal of a more ambitious multiplayer mode, and a cliffhanger ending to the game's campaign mode which was rectified with the release of downloadable content. Among Halo 2's marketing was an early alternate reality game called "I Love Bees" that involved players solving real-world puzzles. Bungie supported the game after release with new multiplayer maps and updates to address cheating and glitches. It was released in November 2004.
Halo 2 was a commercial and critical success. The game became the most popular title on Xbox Live, holding that rank until the release of Gears of War for the Xbox 360 nearly two years later. Halo 2 is the best-selling first-generation Xbox game with more than 8 million copies sold worldwide. The game received critical acclaim, with most publications lauding the strong multiplayer component. In comparison, the campaign and its cliffhanger ending was divisive.
Halo 2 was highly influential for online gaming and cemented many multiplayer in-game features such as matchmaking, lobbies, clan organisation and user emblems. Halo 2 marketing heralded the beginnings of video games as blockbuster media. A port of the game for Windows Vista was released in 2007.
Halo 2 takes place in the 26th century. Humans, under the auspices of the United Nations Space Command or UNSC, have developed faster-than-light slipspace travel and colonized numerous worlds. Human worlds come under attack by a collective of alien races known as the Covenant. Declaring humanity an affront to their gods, the Forerunners, the Covenant begin to obliterate the humans with their superior numbers and technology. After the human planet Reach is destroyed, a single ship, The Pillar of Autumn, follows protocol and initiates a random slipspace jump to lead the Covenant away from Earth. The crew discovers a Forerunner ringworld called Halo. Though the Covenant believe Halo's activation will lead to divine salvation, the humans discover that the rings are actually weapons, built to contain a terrifying parasite called the Flood. The human supersoldier Master Chief Petty Officer John-117 and his AI companion Cortana learn from Halo's AI monitor, 343 Guilty Spark, that activation of the Halos will destroy all sentient life in the galaxy to prevent the Flood's spread. Instead of activating the ring, Master Chief and Cortana detonate the Pillar of Autumn's engines, destroying the installation and preventing the escape of the Flood. Master Chief and Cortana race back to Earth to warn of an impending invasion by Covenant forces.
Halo 2 opens with the trial of a Covenant Elite commander aboard the Covenant's mobile capital city of High Charity. For his failure to stop Halo's destruction, the Elite is stripped of his rank, branded a heretic, and tortured by Tartarus, the Chieftain of the Covenant Brutes. Spared execution, the Covenant leadership—the High Prophets Truth, Regret, and Mercy—give the Elite the chance to become an Arbiter, a rank only bestowed upon Elites in times of crisis. As the Arbiter, the Elite quells a rebellion and recovers 343 Guilty Spark.
On Earth, Fleet Admiral Hood commends the Master Chief and Sergeant Avery Johnson for their actions at the first Halo, with Commander Miranda Keyes accepting a medal on behalf of her deceased father. A Covenant fleet appears near Earth. In the ensuing battle, a single ship carrying the Prophet of Regret slips through Earth's defenses and besieges the African city of New Mombasa. Master Chief assists in defending the city. With his fleet destroyed, Regret makes a hasty slipspace jump, and Keyes, Johnson, Cortana, and the Master Chief follow aboard the UNSC ship In Amber Clad. The crew discovers another Halo installation; realizing the danger the ring presents, Keyes sends Master Chief to kill Regret while she and Johnson find Halo's activation key, the Index.
Responding to Regret's distress call, High Charity and the Covenant fleet arrive at the new Halo, Installation 05, just before the Master Chief kills Regret. The Covenant bombard Chief's location, and he falls into a lake and is dragged away by a mysterious tentacled creature. Regret's death triggers discord among the races of the Covenant, as the Hierarchs give the Brutes the Elites' traditional role as the Prophets' protectors. The Arbiter is sent to find Halo's Index and retrieves it, subduing Johnson and Keyes in the process before being confronted by Tartarus. He reveals that the Prophets have ordered the annihilation of the Elites, and sends the Arbiter falling down a deep chasm.
The Arbiter meets the Master Chief in the bowels of the installation, brought together by a Flood creature called the Gravemind. The Gravemind reveals to the Arbiter that the Great Journey is false, and sends the two soldiers to different places to stop Halo's activation. The Master Chief is teleported to High Charity as the Covenant falls into civil war. The Flood-infested In Amber Clad crashes into the city, and Cortana realizes that the Gravemind used them as a distraction. As the parasite overruns the city, the Prophet of Mercy is consumed. The Prophet of Truth sends Tartarus to Halo with Keyes, Johnson, and Guilty Spark to activate the ring. Master Chief follows Truth aboard a Forerunner ship leaving the city; Cortana remains behind to destroy High Charity and Halo if Tartarus succeeds in activating the ring.
On the surface of Halo, the Arbiter joins forces with Johnson and confronts Tartarus in Halo's control room. When the Arbiter tries to convince Tartarus that the Prophets have betrayed them both, Tartarus instead activates the ring, and a battle ensues. The Arbiter and Johnson kill Tartarus while Keyes removes the Index; the unexpected deactivation sets Installation 05 and all the other Halo rings on standby for remote activation from a place 343 Guilty Spark calls "the Ark." Meanwhile, Truth's ship arrives at Earth, and Master Chief informs Admiral Hood that he is "finishing this fight."
In a post-credits scene, Gravemind assumes control of High Charity. Cortana agrees to answer the Flood intelligence's questions.
A common complaint regarding Halo 2's online play was widespread cheating, which began occurring almost immediately after the game's release. Users exploited bugs in the game and vulnerabilities of the network to win ranked games and thus increase their matchmaking rank.
Some players used "standbying" or "lag killing" to cheat, in which the player hosting the game intentionally pressed the standby button on his or her modem; this resulted in all players except the cheaters freezing in place. This way, the cheater would be given time to freely kill other players or capture objectives. "Dummying" involves using an Elite character and a vehicle, exploiting a glitch which would cause a doppelgänger of the player to appear. Cheating also includes softmodding, in which a player uses devices such as Action Replay and computer programs to gain unfair advantages, and bridging, which uses computer programs to give a player "host" status, and therefore the ability to disconnect other players from the game session. A game exploitation called "superbouncing" or "superjumping" is labeled cheating by many in the Xbox Live community, and Bungie employees have described it as cheating when used in matchmaking. Another exploit called "BXR" allowed players to melee, cancel the animation, and quickly attack for an instant kill; this exploit and many others were removed from the game's sequel.
Halo 2 was unique in that it was one of the first video games to utilize the online gaming capabilities to support Downloadable Content (known as DLCs). This allowed some ideas that were cut during initial production to be completed after release. DLCs alternated between additional multiplayer maps as well as additional story-based content.
The first DLC, Hunt for Truth was released on July 5, 2005. Hunt for Truth's story begins after the events of Halo 2, in which the alien collective known as the Covenant discovers the location of Earth and begins a full-scale invasion of their enemy's homeworld. The supersoldier Master Chief is stowed away aboard an ancient Forerunner ship. On a course set for Earth, he is overwhelmed by a Covenant strike force and rendered unconscious. The Master Chief is captured and interrogated by Covenant forces, but manages to escape using a concealed weapon. The Master Chief attempts to kill the Covenant's leader, Prophet of Truth, but is discovered as he takes aim; Truth escapes as the Chief is left to kill the Prophet's guards and find a way off the ship. Learning that there is no way to change the Forerunner ship's destination, the Chief jumps to Earth using a piece of the vessel as a heat shield.
On March 30, 2007, Bungie announced that two new maps would be available on April 17, 2007. Bungie's own Frank O'Connor confirmed that both Xbox and Xbox 360 users would have access to the content. The two new maps were remakes of maps from the original Halo: Combat Evolved, "Hang em' High" and "Derelict". Due to issues with distribution of the maps, the updates which made the maps mandatory was released on May 9, 2007, later than planned. Bungie also reset all ranks for Halo 2 at the same time. On July 7, also known as "Bungie Day", Bungie released the map pack called the "Blastacular Map Pack" for free.