A greatly improved PEC experience - your character evolves online and offline, in both single-player and multiplayer modes.
Terrorist Leaders are now a strategic target for Rainbow - leaders control respawns, so when you take out the leaders, enemies can no longer respawn.
Terrorists Enemies have a wider variety of reactions and use ballistic shields.
Team Rainbow can use the leap-frogging technique for safely approaching an area defended by an opposing force. Teammates cover each other successively when they move forward.