Call of Duty's iconic killstreak system has been overhauled into a new class-based feature, known as strike packages, for Modern Warfare 3.

But what does that actually mean? Players now choose between one of three strike packages - Assault, Support, and Specialist - and access a different set of rewards based on scoring points in the game. Kills still count, of course, but you also get rewarded for sticking to the objective.

Assault works just like the killstreak system in previous Call of Duty games, with you getting rewards for scoring multiple kills without dying. Like in Call of Duty 4 and Modern Warfare 2, kills with the Assault strike package count towards further killstreaks - a feature Treyarch removed for last year's Call of Duty: Black Ops.

Support, on the other hand, doesn't let your kills stack. The support strike package gives out defensive bonuses that can affect the entire team and, unlike in previous Call of Duty games, your streak is not reset when you die. Finally, the Specialist strike package allows you to create a cocktail of additional perks to give yourself the edge - for every two kills you unlock an additional perk.

It's all about balance, claims joint developers Infinity Ward and Sledgehammer Games. Call of Duty: Modern Warfare 3 is "the most balanced multiplayer experience we have ever done," according to Infinity Ward communications strategist Robert Bowling.

"Killstreaks were a great addition in Call of Duty 4," said Bowling at a media event, but added that "the killstreak system was optimised for one gametype, and that's Team Deathmatch". Strike Packages were conceived, according to Infinity Ward, to provide players with greater flexibility and option in objective-based modes, such as Search & Destroy and Domination.

Here's the full list of options available to the Assault and Support strike packages:

Assault: UAV (3), Care Package (4), I.M.S, Predator Missile (5), Sentry Gun (5), Precision Airstrike (6), Attack Helicopter (7), Strafe Run (9), Little Bird Gunner (9), Reaper (9), Assault Drone (10), AC130 (12), Pave Low (12), Juggernaut (15), Osprey Gunner (17)

Support: UAV (4), Counter-UAV (5), Ballistic Vests (5), Airdrop Trap (5), Sam Turret (8), Recon Drone (10), Advanced UAV (12), Remote Turret (12), Stealth Bomber (14), EMP (18), Juggernaut Recon (18), Escort Airdrop (18)

The Specialist tier allows you to choose between additional perks when you hit your kill milestones, and has a Modern Warfare 3 perk list right here.

Call of Duty: Modern Warfare 3 will be released for Xbox 360, PS3, and PC on November 8.