When Call of Duty first released on October 29, 2003 for the PC, it reshaped the way World War II shooters were done, with on movie-like action and a focus on soldiers as they fought one of the most expansive and influential wars in history. Then the series made video game history again with Call of Duty 4: Modern Warfare by bringing shooters to the modern day. However, the game's greatest influence is arguably through its approach toward multiplayer, with an emphasis on fast-paced, close quarters combat and character progression. We follow the history of multiplayer progressions starting with Modern Ware and ending in the near future with the recent reveal of Advanced Warfare's multiplayer features.

Call of Duty 4: Modern Warfare (November 5, 2007)

By leaving behind the World War II setting and bringing the action to modern day military setting, Call of Duty 4 was not only a landmark game for the series, but it set the standard that other shooters would be judged by. But its influences were not limited to the single player campaign Modern Warfare's take on competitive gameplay would impact how developers regard multiplayer design.

Multiplayer pits S.A.S. against Spetznaz forces using five different classes that include Assault, Spec Ops, Heavy Gunner, Demolitions, and Sniper (the latter two need to be unlocked). The most important and innovative feature is the class progression system, where killing enemy players and getting killstreaks earns experience points unlocks ranks, weapons, and perks. Eventually, players unlocked the Create-a-Class option, where they could mix and match weapons and perks until they developed the ultimate warrior that best suited their play style.

Players that reach the highest level (55) can enter into Prestige Mode, where they trade in their rank, unlocks, and challenge progress for special bonuses. Prestige Mode can be triggered up to ten times, with a special icon denoting each Prestige level. Although Prestige Mode was available on the console release of COD4, it was not included on the PC or Mac versions.

Typical modes are present, such as Free-For-All, Team Deathmatch, and Domination. However, more creative modes that helped the game stand out were Search and Destroy and Sabotage, both of which make use of an explosive briefcase that - in the tradition of Counter-strike - needed to be planted and defended to prevent the opposing team from disarming it. Headquarters mode also put a unique spin on Capture and Hold gameplay by requiring players to defend a position for one minute, then the contested HQ moves to a new location.

World at War (November 11, 2008)

Developed by Treyarch and with a title that was officially revealed on the 64th anniversary of the D-Day invasion (June 6, 2008), World at War would become the last big Call of Duty game to be set in World War II, and it would leave a lasting impression with half the campaign taking place in the Pacific Theater. The game also ended up being the first game set in the Black Ops universe.

Multiplayer Changes:

Competitive multiplayer didn't change too much from Call of Duty 4, except for some balance adjustments and changes to Prestige Mode. The highest level was raised to 65, and Prestige Mode unlocked new bonuses like an additional Create-a-Class slot.

Cooperative (Riding the soldier):

World at War is also the first and last Call of Duty game to feature a full cooperative campaign that supported two players split screen on consoles, or up to four players online. Collecting Death Cards hidden throughout the campaign levels unlocks special abilities in co-op mode, although they can only be activated in private matches. The Wii featured a special type of cooperative mode, where two players shared one screen and a single point of view. The second player essentially "rides" the first player, and can only aim, shoot, and reload. That means the main character essentially has double the firepower, and one player can continue firing at enemies while the other is reloading.

Zombie Mode (Playing with dead things)

Perhaps World at War's greatest multiplayer contribution is the introduction of the Nazi Zombie mode. Beating the campaign on any difficulty unlocks a bonus cooperative multiplayer mode called Nacht der Untoten (Night of the Undead). Four players come together to defend against waves of the undead. Although the mode featured a relatively simple map, and was practically included as a sort of joke, it became so popular that it grew to develop its own universe and canon. Later installments of the World at War zombie mode were ported to iOS as standalone apps. All zombie maps were re-mastered and released as part of the Black Ops Hardened and Prestige Editions, and in the Rezurrection content pack.

World at War Zombie Mode Timeline:

Nacht der Üntoten [German: "Night of the Undead"] (November 11, 2008): Introduced zombie mode gameplay, including the mystery box, where players could trade points in for a random weapon.

[German: "Night of the Undead"] (November 11, 2008): Introduced zombie mode gameplay, including the mystery box, where players could trade points in for a random weapon. Verrückt [German: Crazy] (February 11, 2009): Zombie mode gets seriously crazy with the addition of a German asylum map. The updated brings in higher complexity with the addition of the Perk-a-Cola Machines, which provides players with different perks inspired from the main multiplayer game. Players are tasked with the objective or turning on the power in addition to fending off the undead, which turns on the Perka-a-Cola machines and the newly introduced Electro Shock Defenses.

[German: Crazy] (February 11, 2009): Zombie mode gets seriously crazy with the addition of a German asylum map. The updated brings in higher complexity with the addition of the Perk-a-Cola Machines, which provides players with different perks inspired from the main multiplayer game. Players are tasked with the objective or turning on the power in addition to fending off the undead, which turns on the Perka-a-Cola machines and the newly introduced Electro Shock Defenses. Shi No Numa [Japanese: "Swamp of Death"] (June 11, 2009) - Shi No Numa is the only World at War map to feature Japanese Zombies, particularly ones from the Japanese Imperial Army. The map takes place in a secret Japanese facility, located in a swamp and surrounded by dense jungle. It also introduces a number of new elements, most notably a special round where players must combat a special zombie. Hellhounds, zombified dogs that spawn from within the map instead of coming from outside of it, are also introduced here.

[Japanese: "Swamp of Death"] (June 11, 2009) - Shi No Numa is the only World at War map to feature Japanese Zombies, particularly ones from the Japanese Imperial Army. The map takes place in a secret Japanese facility, located in a swamp and surrounded by dense jungle. It also introduces a number of new elements, most notably a special round where players must combat a special zombie. Hellhounds, zombified dogs that spawn from within the map instead of coming from outside of it, are also introduced here. Der Riese [German: "The Giant"] (August 6, 2009): Set in a secret Nazi facility in Lower Silesia near Breslau, Germany (now Wroclaw in Poland), Der Riese is the final zombie map released for World at War. Players are trapped in a secret Nazi factory, and once again they have to turn the power on to survive. The mode is significantly stepped up with teleporters (which are turned on with the power switch) and the Pack-a-Punch Machine that upgrades a player's weapon for to a better version for 5,000 points (unlocked when the power is turned on and all three teleporters are linked).

World at War DLC Timeline

Map Pack 1 (February 11, 2009): Knee Deep; Nightfire; Station. Zombie mode: Verruckt.

(February 11, 2009): Knee Deep; Nightfire; Station. Zombie mode: Verruckt. Map Pack 2 (June 11, 2009): Banzai; Corosion; Sub Pens. Zombie mode: Shi No Numa.

(June 11, 2009): Banzai; Corosion; Sub Pens. Zombie mode: Shi No Numa. Map Pack 3 (August 6, 2009): Battery; Revolution; Breach. Zombie mode: Der Reise.

Modern Warfare 2 (November 10, 2009)

Although World at War was well received, Call of Duty 4 left fans clamoring for another modern military shooter. In 2009, Infinity Ward delivered, but not without some controversy. The airport mission, "No Russian," involves the massacre of civilians, which makes Modern Warfare 2 one of the most controversial games in the series. The developers saw fit to include an option to skip the scene, however public outcry wasn't limited to the single-player campaign content.

Multiplayer Changes (Cannot connect to server)

Modern Warfare 2's multiplayer is an evolution of Call of Duty 4, with new Create-a-Class equipment, HUD improvements, the inclusion of Mosh Pit (a random combination of all game modes except 3rd Person Cage Match), and fifteen special killstreak bonuses to choose from. Players could equip up to three killstreak perks that ranged from getting a supply drop, to guiding in a Predator missile, or controlling an AC-130 gunship.

However, at the same time, multiplayer seemed to devolve on the PC side, and stirred up quite a bit of controversy. It was revealed that the game would not have dedicated server support (which eliminated custom mod support), and instead of allowing for 64 players like previous games, it would be limited to 18 player (9v9) matches like the console releases. Lastly, there was no way to vote towards kicking or banning cheating players. This change angered a lot of PC gamers, since it was clear that consoles were setting the standard for PC gaming instead of the other way around, and the Battlefield developers immediately seized on the opportunity to win over upset players.

The controversy almost overshadowed the fact that Modern Warfare 2 is the first Call of Duty game to use Steamworks. The IWNET multiplayer service on the PC uses Steam as its backbone and the Punkbuster anti-cheat system was replaced by Valve Anti-Cheat. It was a double-edged sword, since Steam wasn't yet fully embraced by the majority of PC gamers. The Valve Anti-Cheat system didn't require an administrator to police the game, but it was designed to punish cheaters, not prevent it, by banning them after a random delay. The anger from PC gamers pretty much went unanswered, as Modern Warfare 2 surpassed its predecessor's first week's sales. Although there was a steep decline in PC sales afterwards, the anger largely died down and people learned to accept the game. However, in May 2010, hackers managed to unlock the developer console and recreated the effect of dedicated servers.

Cooperative (Special Operations):

Instead of having a full cooperative campaign like World at War, Modern Warfare 2 introduced a mode called Special Ops. These are a series of independent missions that take place across a variety of locations and support up to two players. Missions include a snowmobile race between two players, and one where a player fires from an AC-130 while the other fights from the ground.

Downloadable Content (The premium blend)

Modern Warfare 2 is also the first game to offer premium multiplayer packs on the PC. All three World at War Map Packs were available for free on PC through patches, and sold for around ten dollars on consoles. Now multiplayer DLC packs would be priced at $15 for all systems - a price that has not changed in over four years, even after the price of the main game was reduced to $19.99. It also marked the start of Call of Duty's relationship to the Xbox system. All DLC packs from this and future games would release for the Xbox 360 roughly 30 days in before all other systems.

Modern Warfare 2 DLC Timeline:

Stimulus Package (March 30, 2010 [Xbox 360]; May 4, 2010 [PS3, PC]): Crash; Overgrown; Bailout; Salvage; Storm

(March 30, 2010 [Xbox 360]; May 4, 2010 [PS3, PC]): Crash; Overgrown; Bailout; Salvage; Storm Resurgence Package (June 3, 2010 [Xbox 360]; July 6, 2010 [PS3, PC]): Carnival; Trailer Park; Fuel; Vacant; Strike

Black Ops (November 9, 2010)

It's Treyarch's turn to produce a Call of Duty game again, and it takes a decidedly different approach with Black Ops. The game is generally regarded as a sequel to World at War, since the storylines share a common connection. Beyond that, the story is completely blown out, complete with an opening sequence from The Bay of Pigs invasion, where the player tries to assassinate Fidel Castro. Then there's Vietnam and The Cold War, all tied together with a mind boggling conspiracy.

Multiplayer changes (Care to make a Wager Match?):

Multiplayer is similarly over-the-top with a reinvented progression system. Instead of unlocking equipment and perks through leveling, players earn an in-game currency called CODPoints through playing matches and completing Contracts. These points can then be used to purchase multiplayer upgrades, however some options remain locked until players reach a certain level. Create-a-Class 2.0 allows players to modify the appearance of their characters, including face paint and gun camouflage, in addition to the loadout.

Black Ops is also the first game to include Combat Training, so new players could practice against AI opponents before jumping into the real deal. However, killstreaks earned in training mode still earns points, so many players use it as a quick way to unlock equipment.

Two new systems are introduced in Black Ops: Contracts and Wager Match. Players can purchase a contract, which directs them toward an objective during a multiplayer match. Completing a Contract can earn a lot of CODPoints, however each Contract has a time limit, and players lose out if it expires before they're able to complete the objectives.

Wager Matches let players gamble with their CODPoints across a number four specialized game modes. Each player can buy in using 10, 1,000, or 10,000 CODPoints, but only the top three players win the prize. Wager Match modes include One in the Chamber, where each player has a gun one bullet in it and a knife. Getting a single hit from either weapon kills the player. Sharpshooter gives everyone the same weapon, which changes every 45 seconds. Getting consecutive kills earns perks and score multipliers. Sticks and Stones gives every player a crossbow, a knife, and a tomahawk. The trick is, you lose all your points if you're killed with a tomahawk. Lastly is Gun Game, where every player starts with a Python. Every kill moves the player up one tier and grants a better gun. The first player that manages to kill using all 20 weapons wins. However, getting killed by a knife or committing suicide will move the player down a rank.

Black Ops is the first game to use Theater Mode, where players can capture screenshots or record clips from their games to watch later and share online. Viewers have full control over the viewing, including pause, fast forward, rewind, and slow play. Although Theater is included in both Black Ops games and Modern Warfare 3, it is missing from Ghosts. However, it's expected to make a return in Advanced Warfare.

Zombie mode (Hollywood undead):

It wouldn't be a Black Ops game without Zombie Mode, and Treyarch enthusiastically embraces this fact. In addition to the zombie map Kino Der Toten (Theater of the Dead), completing the game or inputting a cheat code into the computer from the main menu unlocks the Dead Ops Arcade (DOA), which is a retro top-down shooter in the theme of zombie mode from World at War and Black Ops. A similar process also unlocks "Five", which is a zombie map that takes place in The Pentagon and features real-life figures from the Cold War such as John F. Kennedy, Robert McNamara, Fidel Castro, and Richard Nixon as playable characters.

As though that weren't enough, zombie mode reached an unprecedented high point with Call of the Dead, which is included in the Escalation Content Pack (May 2011). In it, players take the roles of characters with the likeness and voices of real-life celebrities such as Sarah Michelle Gellar (Buffy the Vampire Slayer), Robert Englund (A Nightmare on Elm Street), Danny Trejo (Machete), and Michael Rooker (The Walking Dead). Together, they have to overcome the zombie hordes and an superpowered undead version of legendary writer and director, George A. Romero - the godfather of the zombie genre. A key Wonder Weapon is introduced with Call of the Dead, the V-R11, which can transform zombies back into humans. These humans can either be killed permanently by players, serve as a yummy distraction for the zombie horde and Lightning Monster Romero, or they'll just freak out and commit suicide in the icy waters. The weapon can also be used to temporarily calm George Romero down, or supercharge a teammate so that s/he is immune to zombie attacks and does infinite damage.

The final Black Ops DLC pack, Rezurrection (August 2011), features re-mastered versions of the original World at War zombie maps. So, players could relive the experience using all the Black Ops weapons, gameplay, and perks. The DLC also included a new map that took players to the moon, where they could hunt zombies in reduced gravity. The pack also has a creepy zombie soundtrack and Moon theme. Rezurrection was free for Black Ops Hardened and Prestige Edition owners.

Black Ops DLC Timeline:

First Strike Content Pack (February 1, 2011 [Xbox 360]; March 3, 2011 [PS3]; March 25, 2011[PC]): Berlin Wall; Discovery; Kowloon and Stadium. Zombie map: Ascension.

(February 1, 2011 [Xbox 360]; March 3, 2011 [PS3]; March 25, 2011[PC]): Berlin Wall; Discovery; Kowloon and Stadium. Zombie map: Ascension. Escalation Content Pack (May 3, 2011 [Xbox 360]; June 2, 2011 [PC]; June 9, 2011 [PS3]): Zoo; Convoy; Hotel; Stockpile; Zombie map: Call of the Dead.

(May 3, 2011 [Xbox 360]; June 2, 2011 [PC]; June 9, 2011 [PS3]): Zoo; Convoy; Hotel; Stockpile; Zombie map: Call of the Dead. Annihilation Content Pack (June 28, 2011 [Xbox 360]; July 28, 2011 [PS3, PC]: Hangar 18, Silo, Hazard, Drive-in. Zombie map: Shangri-La.

(June 28, 2011 [Xbox 360]; July 28, 2011 [PS3, PC]: Hangar 18, Silo, Hazard, Drive-in. Zombie map: Shangri-La. Rezurrection Content Pack (August 23, 2011[ Xbox 360]; September 22, 2011 [PS3, PC]): Re-mastered zombie maps: Nacht der Untoten; Verruckt; Shi No Numa; Der Reise. New zombie map: Moon. Also includes: Soundtrack, Moon theme.

Call of Duty's evolution isn't done yet. The timeline continues and heads into the future in part 2.