Scorestreak

The Scorestreak system is a multiplayer mechanic introduced in Call of Duty: Black Ops II, replacing Killstreaks and Strike Chains. In this system, rewards are earned based on the amount of score one earns in a single life.

Overview
In previous Call of Duty games, players were allowed to bring up to three rewards with them to be earned after earning a certain amount of kills or earning a certain number of points. However, players now earn rewards for earning a certain amount of score  in a single life. This means actions like kills, captures, completing objectives, shooting down enemy air support, assists, and assists with certain scorestreaks count towards the earning of new scorestreak rewards. Nevertheless, the streak ends upon death. The Player's Scorestreak rewards can be obtained multiple times in one life, but only if the player uses his scorestreak prior to receiving the same scorestreak again. For example, if the player chooses the Swarm scorestreak, chooses to save it and his scorestreak loops around to the Swarm again, the first Swarm will be lost, being replaced by the second Swarm received.

Contrary to most previous games, dying does not impede progression by called in streaks. While any points gained are lost upon death, the player may still recieve points through streaks called in before being killed or by calling in streaks left. As long as points are awarded afterdeath, it doesn't matter when a scorestreak has been called in nor when it has been earned.

Using the perk Hardline, the score needed for each scorestreak is decreased by 20% meaning this perk is extremely beneficial for obtaining the higher rewards. For example, using hardline, you will only require to achieve a 1585 score streak rather than 1900. This equates to almost 3 kills less in team-death match and domination excluding bonus score for objective play and assists.