The game employs a cover and movement system not unlike those featured in Gears of War and Brothers in Arms: Hell's Highway, wherein the player can quickly choose to dodge between different forms of cover, coming out only to fire shots at enemies. Staying in cover is advantageous, as the player only regenerates health when they have not received damage for a certain amount of time (as in the Halo and Call of Duty games). Although players initially are only equipped with an M4 carbine, other weapons such as the RPG-7 and M79 grenade launcher, Remington 870 shotgun, and M249 SAW as well as various types of grenades (Flash and fragmentation) are acquired throughout the game. Enemy A.I. is relatively strong, both keeping track of the player's location realistically (that is, not omniscient but using sight and sound to locate the player) as well as actively pursuing and flanking them when cover is sought by the player.
Plot
Twelve years after Judgment Day, John Connor reflects on the old days of preparing for the future battle. Returning to an evac point with Blair Williams and other soldiers, they battle their way through machines to discover that there are no helicopters waiting for them. Escaping in trucks instead, the group is attacked by a Hunter-Killer aircraft. After John Connor manages to destroy the H-K, a T-600 appears and kills several members of his team.
The team travels underground, then above again, battling machines. The surviving trio manages to reach the evacuation point, meeting soldiers. Aerostat drones attack, and John, Blair and others go outside to take care of them. One is killed in the battle. A Resistance team led by soldier David Weston (Sean Cory Cooper) asks for help, but his transmission is lost. The team then tries to make a landing place for a helicopter. The chopper lands and rescues the team, but John and Blair stay behind to rescue David's team. The duo goes into the sewers.
A rescue team, Epsilon, has a helicopter going down, so the duo goes to its crash-site to check for survivors. They rescue four soldiers, Angie (Rose McGowan), an unknown, Deckard (Joe Camareno) and Dobkin (Nolan North). They fight a legion of machines and then, afterwards, decide to head for an old Resistance outpost. Deckard and the unknown are killed by a T-600, and the team is forced to retreat. They manage to destroy two T-600s. They have no choice but to retreat, but with no way out, the team is forced to destroy the T-600s, though Dobkin is mortally wounded in the fight.
The three continue to go to Skynet while defending themselves. They decide to go to a tower so they can observe Skynet patrols so as to plan a route to rescue David. They encounter T-600s with rubber skin, which the trio destroy. John warns the other two about the T-800, which has real, vat-grown skin. They reach the tower, where they encounter a Hunter-Killer, but John, Blair and Angie manage to destroy it. There are too many machines on a nearby street that they planned to go down, so the three decide to go to Union Station at the subway, following the tracks to Skynet.
They traverse their way to a hidden survivalist camp. The survivalists don't trust them at first (because of the T-600s with rubber skin), but they manage to gain their trust. They say they have not encountered Skynet for a long time. The leader, named Warren Campbell (Ed O' Ross), leads him to Barnes (Common), who will supply them. Machines come, and John, Blair and Barnes fight off the machines while Warren and Angie evacuate the area. Barnes reveals to John that machines actually come every two months. They destroy the machines with detonators, and everybody evacuates by train. John and Blair defend the train by missile launcher. They stop to rescue other people from machines and succeed. They escape, but the train derails, so they go on foot to a truck depot, meeting up with other soldiers. Warren drives a school bus, while John and Blair defend it, eventually saving the bus. They go their separate ways, but Warren says they can visit them anytime. Warren still has doubts of their plan, saying that they can't communicate as long as a Skynet communications tower still stands. Barnes joins the three, saying he's tired of running and wishes to join the Resistance.
Battling numerous machines to infiltrate the Skynet compound, an alarm is accidentally triggered when Connor steals important documents. While Barnes sets up explosives, John, Blair and Angie old off T-600s and T-7-T's. While the explosives go off, they run into the elevator to escape. However, with the control panel located outside, Angie sacrifices herself so that John and the others can return to the surface. John is racked with guilt, but Blair explains that he had helped Angie fight, and she believed he could help humanity win.
