What is new in Call of Duty: Modern Warfare 3?

In a breif awnser

New single player missions carrying on where we ended MW2

Two new online game modes

Kill confirmed - Pick up dog tags of killed enemies to be credited with the kill or freindlys to deny the kill

Team Defender - First person who dies drops a flag the team who holds it longest wins

Kill streaks redesigned and a new form added where every 2 kills you get a new perk and at 8 you get all perks unlocked (Hardline does affect this meaning 7 kills for all)

New Spec ops missions ( Can be done on and offline)

And survival mode ( Can be done on and offline) - players fighting endless waves of enemies with each wave getting more difficult

Along with this weapons now have a thing called Proficiency where you have to level your gun up by using it to unlock things such as reduced kick and impact

Single Player features a fresh story.

You will engage enemy forces in New York, Paris, Berlin and other attack sites across the globe. The world stands on the brink, and Makarov is intent on bringing civilization to its knees. You will assume the role of various characters, changing perspectives throughout the story.

— From: Call of Duty: Modern Warfare 3

The game will see the return of Task Force 141 Captain John "Soap" MacTavish, former SAS Captain John Price and Russian informant Nikolai who are on the run after killing the rogue U.S. Army Lieutenant General Shepherd. Russian Ultranationalist Vladimir Makarov will also reprise as the game's primary antagonist.

New non-playable characters that have been confirmed so far include Truck and Grunt, who form part of the Delta Force fire team alongside Frost and Sandman. A Delta Force operative named Grinch was also announced.

Multiplayer gets a serious buff!

Killstreaks have been redesigned, new game modes are being introduced, and a gun progression system evolves your weapons over time. Along with new perks, 16 maps and enhanced private match customization, multiplayer has been completely re-balanced and polished into the most intense and rewarding experience possible.

Killstreaks have been redesigned.

Killstreaks have been transformed into Pointstreaks, now rewarding players both for landing kills and completing objectives. Additionally, they have been broken up into three different categories, known as Strike Packages:

Assault
Pointstreaks within this package chain together and deal direct damage. It includes classics like the Predator Missile and Attack Helicopter. Your streak resets on death.

Support
Pointstreaks within this package do not chain, focusing instead on surveillance and disruption. Your streak does not reset on death.

Specialist
Pointstreaks within this package are designed for advanced players. Rewards come in the form of additional perks for optimal performance. These perks last until death.

Weapons are more proficient.

Weapons now rank up through use, unlocking additional attachments, reticules, camos and the new proficiency category. Weapon Proficiencies allow you to specialize your weapons with helpful attributes, such as Kick for reduced recoil and Impact for deeper penetration through hard surfaces.

Modes and maps can be customized.

All sixteen maps have been optimized for natural movement and intense combat. Each environment presents its own strategies and challenges, and a diverse collection of locales keeps every match fresh and interesting.

Along with the return of the fan favorites, several new game modes have been introduced. Collect dog tags from killed players in Kill Confirmed mode and prevent the other team from grabbing yours. In Team Defender mode, grab the flag and protect the flag carrier to increase your team’s score. Along with six new private match modes, multiplayer opens up a variety of entirely new scenarios.

— From: Call of Duty: Modern Warfare 3

Spec Ops will also return...

Spec Ops will feature up to 48 stars, unlike Modern Warfare 2, which featured 69 stars. Some weapons in Spec Ops will be exclusive to Spec Ops and will not be available for play in multiplayer.

Earn experience and rank up with the newly implemented progression system. The higher the rank, the more weapons, air support, and gear armories you will have available to customize so you can change your tactics on the fly. In addition to the action packed battle for freedom, the cooperative Survival Mode also serves as an effective training tool for competitive multiplayer action.

— From: Call of Duty: Modern Warfare 3

Defeat endless waves of monsters in the new Cooperative Mode!

Call of Duty: Modern Warfare 3 will feature a new Survival Mode. Survival Mode features one to two players fighting endless waves of enemies with each wave getting more difficult. The mode will be available on all multiplayer maps in the game and in the mode, players can earn "cash" for items such as weapons, upgrades and ammo.

Cooperative Mode can be found under Spec Ops...

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