Call of Duty is a video game based on the Quake III Arena engine (id Tech 3), and was released on October 29, 2003. The game was developed by Infinity Ward and published by Activision. The game simulates the infantry and combined arms warfare of World War II. Call of Duty was accompanied in September 2004 by an expansion pack, Call of Duty: United Offensive, which was also produced by Activision, but developed by Gray Matter Interactive with contributions from Pi Studios. The game follows the American paratroopers, British paratroopers and the Red army. The Mac OS X version of the game was ported by Aspyr Media. In late 2004, the N-Gage version was developed by Nokia and published by Activision. Other versions were released for PC, including Collector's Edition (with soundtrack and strategy guide), Game of the Year Edition (includes game updates), and the Deluxe Edition (which contains the United Offensive expansion and soundtrack; in Europe the soundtrack was not included). Since November 12, 2007, Call of Duty and its sequels have been available for purchase via Valve's content delivery platform, Steam.

Call of Duty 2 is a first-person shooter video game and sequel to the critically acclaimed game Call of Duty. It was developed by Infinity Ward and published by Activision. The game is set during World War II and is experienced through the perspectives of soldiers in the Red Army, British Army and United States Army. It was released on October 25, 2005 for PC, June 13, 2006 for Mac OS X and November 15, 2005 for the Xbox 360. Other versions were made for mobile phones, Pocket PCs, and Smartphones.

Call of Duty 3 is a World War II first-person shooter and the third installment in the Call of Duty video game series. Released on November 7, 2006, the game was developed by Treyarch, and was the first major installment in the Call of Duty series not to be developed by Infinity Ward. It was released on the PlayStation 2, PlayStation 3, Wii, Xbox, and Xbox 360. Call of Duty 3 follows the American, Canadian, British, French Resistance and Polish armies after D-Day in the Falaise Gap.

Call of Duty 4: Modern Warfare is the fourth installment of the main series, and was developed by Infinity Ward. It is the first game in the series not to be set during World War II, as well as the first to receive a Mature rating from the ESRB (except for the Nintendo DS version, which was rated Teen). The game was released for Microsoft Windows, Nintendo DS, PlayStation 3, and Xbox 360 on November 7, 2007. Download and retail versions for Mac OS X were released by Aspyr in September 2008. As of May 2009, Call of Duty 4: Modern Warfare has sold over 13 million copies.

Call of Duty: World at War developed by Treyarch is the fifth installment of the main series, and returns to the World War II setting of earlier titles. On June 9, 2008, it was confirmed that the game would be titled Call of Duty: World at War and would be set in the Pacific theater and Eastern front of World War II. The game uses the same proprietary game engine as Call of Duty 4. Call of Duty: World at War was released for the PC, PS3, Wii, Xbox 360 consoles and the Nintendo DS handheld in North America on November 11, 2008, and November 14, 2008 in Europe. As of June 2009, Call of Duty: World at War has sold over 11 million copies.

Call of Duty: Modern Warfare 2[13] is the sixth installment of the main series. It was developed by Infinity Ward and published by Activision. Activision Blizzard officially announced Modern Warfare 2 on February 11, 2009. The game was released worldwide on November 10, 2009, for the Xbox 360, PlayStation 3 and Microsoft Windows. A Nintendo DS iteration of the game, titled Call of Duty: Modern Warfare: Mobilized, was released alongside the game and the Wii port of Call of Duty : Modern Warfare. Modern Warfare 2 is the direct sequel to Call of Duty 4 and continues the same storyline, taking place five years after the first game and featuring several returning characters including Captain Price and "Soap" MacTavish.

Call of Duty: Black Ops is a 2010 first-person shooter video game developed by Treyarch and published by Activision for release on November 9, 2010.[10] Officially announced on April 30, 2010, the game is the seventh installment of the Call of Duty series, the third game in the series to be developed by Treyarch, and the first game to take place during the Cold War and partially in the Vietnam War. It was initially only available for pre-order on PC, Xbox 360, and PlayStation 3; however, Activison has since confirmed that it will also be released for the Nintendo Wii as well as the Nintendo DS.

Call of Duty: Modern Warfare 3 is an upcoming first-person shooter video game. It will be the eighth installment of the Call of Duty series and the third installment of the Modern Warfare series. Due to a legal dispute between the game's publisher Activision and the former co-executives of Infinity Ward which caused several lay-offs and departures within the company Sledgehammer Games will assist in the development of the singleplayer, and Raven Software will develop the multiplayer. The game is said to have been in development since only two weeks after the release of their previous game, Call of Duty: Modern Warfare 2. Sledgehammer is aiming for a "bug free" first outing in the Call of Duty franchise, which also sets a goal for Metacritic review scores above 95 percent. On May 12, 2011 on the official YouTube page for the Call Of Duty franchise, four teasers were released entitled: America, England, France and Germany, indicating possible location for the game. The "e" in each name was stylised in the trailers with a Modern Warfare stylised number "3".

Before being switched to become the co-developers of Modern Warfare 3, Sledgehammer games were already working on a Call of Duty game. This game was announced before Modern Warfare 3 and after Black Ops, however, no details were released. The game was said to be an action-adventure first-person shooter video game. A Call of Duty MMO was also rumored to be in development. Activision CEO, Eric Hirshberg, later stated that Modern Warfare 3 was not the same title as Sledgehammer Games action-adventure Call of Duty game. When asked if the action-adventure game was also in development, Hirshberg then stated that the Sledgehammer team was fully focused on Modern Warfare 3 and that their own title had been put on hold.

COD1 - Unknown to me (comment if you know)

COD2 - Unknown to me (comment if you know)

COD3 - Unknown to me (comment if you know)

COD4 - 13,000,000

COD5 - 11,000,000

COD6 - 20,000,000 (4.7 million on first day)

COD7 - 18,000,000 (5.6 million on first day)

COD8 (estimated) - 16,000,000

Storyline.

Dr. Maxis and his scientist team, Group 935, were tasked with creating an army of super soldiers and new technology for the government project christened "Der Riese" or "The Giant". In his experiments, Maxis used Element 115 to create the zombies. The zombies, however, couldn't be controlled and would always be killed when they went berserk.

While this was going on, Richtofen was testing 115 on living test subjects to create his super soldiers at a Siberian facility. In his experiments, Richtofen used Takeo, Nikolai Belinski, and an unknown Mexican. When Richtofen accidentally killed the Mexican, he replaced him with Dempsey. Dempsey had recently been captured when he led a Marine Recon team to an abandoned asylum to rescue Dr. Peter McCain, an OSS spy sent to infiltrate Group 935. Peter, however, had already been discovered, along with Harvey Yena. The testing affected each of the subjects' minds, making Dempsey extremely aggressive, quieting Takeo into only reciting Japanese proverbs, and making Nikolai functionless without vodka. It also had the side effect of erasing their memories, although, some still possess a few memories.

Maxis also invented 115-powered teleporters, but they would always destroy anything sent through them. All of these experiments were done with his assistant, Dr. Richtofen. Without Maxis, Richtofen and Schuster would complete the first successful teleportation with a walnut using a very small amount of 115. When Maxis found out about this, he criticized Richtofen for not working on his project and that teleporting a walnut wasn't a big deal. Maxis then told Richtofen that he was going to make a deal with the Nazi party for money and equipment in exchange for weapons. These new weapons Group 935 created were also powered by 115. Maxis created the Ray Gun based on plans received from Shi No Numa. Richtofen created the Monkey Bomb and Wunderwaffe DG-2 from 115. Maxis promised to mass-produce the DG-2 to his superiors, but his growing infatuation with Sophia slowed his progress and infuriated Richtofen, who was secretly plotting to overthrow him and take control of Group 935. Richtofen continued his teleporter tests with Schuster behind Maxis' back. Richtofen was the first human test subject and was first sent to the M.P.D., which he believed to be of alien origin. When he touched it, he felt static and started hearing whispering. He was then teleported to a jungle. Dr. Scheuster got worried and planned to scrap the teleporter when Richtofen had been gone for a few days, but he returned as Scheuster was talking about it and told him that there was work to be done. Richtofen sounded much crazier and Scheuster noticed this change.

Two Group 935 scientists, Dr. Groph and Dr. Scheuster, were stationed at the Moon base and were trying to figure out how to work the M.P.D.. When Scheuster killed a rat, its soul was absorbed by a glass vial protruding from the machine. The pair then proceeded to kill many people until the device was filled with souls. The bodies were buried on the moon, leaving them open to zombification. When they finished, they contacted Richtofen who told them that he was going finally going to get rid of the Maxises, indicating that the two scientists were aware of his scheme.

Unbenounced to Maxis that Richtofen had already mastered teleportation Maxis was still trying to master it. Maxis was getting frustrated that he could not send a subject to the mainframe Maxis then used his daughter Samantha's dog, Fluffy, as a teleporter test subject but once again failed. The dog was teleported, but instead of being destroyed like past test subjects, she was zombified (the first hellhound). When Samantha came running in and started questioning her dad about what happened to her dog, Maxis tried to stop her and get out of the room. Richtofen then followed through with his previously-planned betrayal by locking Maxis and his daughter in the room with the hellhound, he then activated the teleporter think which then killed Samantha and Maxis.

Little did Richtofen know that the teleporter actually worked and sent Samantha to the Moon base. In her fear, she ran into the M.P.D. and became the one to control the zombies. When Richtofen was informed of what had occurred he warned the pair of scientists about the hellhound and then told them to find a way to get Maxis. When Maxis was found, they let him approach his daughter to calm her down. After apologizing for his actions, Maxis told Samantha to kill all of the Group 935 members for betraying him and was subsequently shot. Samantha then proceeded to fulfill her father's request by unleashing the zombies.

Richtofen retreated with his super-soldiers to Shi No Numa to think things through. When the zombies attacked Richtofen he realized that Samantha will stop at nothing to seek revenge. Richtofen planed to recover all of the equipment to take control control of the zombies. Richtofen then took the group to Der Riese, which had been abandoned since the zombie takeover. The group used the Wunderwaffe DG-2's 115 to overcharge the Teleporter, making it capable of time travel. Richtofen was apparently unaware of this possibility until he tried it. He seemed unconcerned that he and his partners have been teleported to an abandoned theater in Germany in an unknown year. Although he didn't know what year it was, Richtofen knew about the theater as it was the place Maxis would unveil the Teleporter to the German high command. Since Maxis was killed, the theater was abandoned.

Sometime prior to Ascension, Yuri Kravcheski was transferred to work on sending monkeys into space, much to his dismay. His transfer was caused by his superior, Gersch, who he holds a grudge against. As the radio messages progress, Yuri notices the teddy bear and the Matryoshka Dolls and wonders how a child could be let into the station. A child then slowly drives Yuri insane. Yuri, in his state of insanity, finishes the Gersch Device and has Gersch activate it, letting in the zombies and trapping Gersch. Yuri soon realizes his mistake and is heard screaming at the end of the last recording.

After the events of Kino der Toten, the main characters somehow reach the abandoned Soviet launch pad in Ascension. When the game starts, the four are landing in the starting room on the lunar lander as the color turns to black and white (which the characters acknowledge). The characters then hear Gersch, who tells them that the mechanism must be repaired. He is referring to the Kassimir Mechanism, which must be repaired by completing different tasks. After all of the tasks are completed and the mechanism is repaired, Gersch is freed.

While the events of Ascension are occurring in Russia, the events of "Five" are also unfolding in the Pentagon. A piece of Intel reveals that all Wunderwaffe materials were to be moved to American-controlled installations. As a mainframe is visible behind one of the windows in "Five", it is apparent that it was moved there as per this order. While John F. Kennedy, Robert McNamara, Fidel Castro, and Richard Nixon are negotiating, zombies break into the Pentagon with only the four of them left to fight them. While fighting, they call the characters in Ascension using three red telephones spread across the Pentagon.

As they continue fighting, the three super-soldier test subjects slowly regain their memories. Takeo is the first to remember, and remarks to himself that some day when the group is finished fighting zombies Richtofen will get what he deserves. He also shows his observations of the other two. He believes Nikolai drinks vodka because he wishes to forget the past and can't function when he remembers it, perhaps meaning Nikolai is beyond hope. Tank, on the other hand, is slowly making progress, as he remembers that he'd seen Richtofen before the fight at Shi No Numa. Takeo notes his shifting memories and believes Tank is finally remembering what Richtofen did to him.

Sometime in the present, George A. Romero stumbled upon Group 935's research while making a WWII film. He and the cast took a ship out to an abandoned lab in Siberia. After he and the ship's crew were zombified, only the cast, made up of Sarah Michelle Gellar, Robert Englund, Danny Trejo, and Michael Rooker, remained. This set the stage for Call of the Dead. After the Kassimir Mechanism was completed in Ascension, it overloaded the teleporter and sent the original characters to a Group 935 facility in Siberia, where they were trapped behind a locked door. The celebrities then proceeded to help them escape to Paradise. Richtofen then asked the celebrities to help him obtain the Golden Rod, which they did. Richtofen thanks the group by giving them the DG-2 to help them fight the zombies. In reality, the group could've escaped after the security system was disabled. It is unknown what became of the celebrities after helping the group escape.

Shangri-La, however, does not live up to its name, as its inhabitants have all been zombified before the group's arrival. Richtofen now states that this the last step to controlling the world before he is teleported there. The temple houses a mining facility filled with Element 115, explaining the inhabitants' zombification.

Prior to the group's arrival to Shangri-La, two explorers, Brock and Gary went on an expedition to prove their theories on Argatha. Brock later figures out that the temple wasn't built by an ancient civilization, but by people in the modern era interpreting it. After investigating the temple, the pair accidentally activated the temple's time travel and died in the resulting Zombie attack. The group travels back in time and helps the pair survive. The pair's changing fate is illustrated by the radio that changes message and location as the group helps them. When the group finally create the Focusing Stone, it lands on an altar with Richtofen's name on it, meaning the temple was in fact another Group 935 facility and explaining Richtofen's knowledge of its location. The two explorers are then sent back to the moment they discovered the temple, indicating that they're stuck in a never-ending loop.

Now in possession of both the Golden Rod and the Focusing Stone, Richtofen believes he can now control the zombies. The group then travels to Area 51 so they can get to the moon via a teleporter to a top-secret Moon facility named Griffin Station. Due to the Element 115 on the moon, astronauts and scientists sent there have been zombified before the group's arrival. The people killed by Groph and Scheuster contributed even more to the zombie horde.

Richtofen then has the group complete the M.P.D.. When the device is completed, it opens up to reveal Samantha Maxis suspended in the air. As it turns out, the device acts like a prison and keeps her cryogenically frozen so she can be used to control the zombies. Richtofen goes to a terminal to power up the Golden Rod (or V Device) and the Focusing Stone, which he fuses together. However, he encounters Dr. Maxis inside the terminal, who tries to stop him. Richtofen switches souls with Samantha to gain control of the zombies. Richtofen finally thinks everything has gone his way, until Takeo, Tank, and Nikolai decide to stop him. Dr. Maxis, sensing Richtofen's betrayal, prepared a backup plan in case Richtofen got this far. (He even referred to Richtofen by name in his radio message.) The group then fires the missiles located on the moon which destroy the earth's atmosphere. Richtofen is now only in control of the zombies on the moon, greatly lessening the damage he could cause.