Titanfall takes place across a series of planets in which the global corporation, the IMC, is trying to gain power over the people. A rebellious force arises to fight them of called the Militia. While the Militia is made up of regular troops fighting for their home and trained pilots, the IMC is made up of hired mercenaries and robots.
The campaign follows the journey of rifeman Jack Cooper, a rifleman in the Militia. While being trained to be a pilot by pilot Lastimosa. On a deployment to a planet, a suprise attack is launched on them and Lastimosa is killed, leaving Cooper and Lastimosa's titan, BT-7274 to complete his mission.
Throughout the campaign you are tested by having to fight as both a pilot on his own and as a titan. You have to fight on multiple terrains and with many variables involved restricting the way you play. All of this combined with the immersive storytelling makes the characters very close to you.