Semper Fidelis

Semper Fidelis is the first mission in Battlefield 3.

Synopsis
The player, as Henry Blackburn, starts out in the middle of a New York city street overlooking a subway system. After hearing some police sirens, Blackburn dives onto the the train, and barely manages to grab onto one of the car edges as he slides off the top. He swings in, landing upon and subsequently killing several PLR insurgents with an M9. After doing so, Solomon can be heard in the background telling his insurgents to kill the passengers on the train, explaining that "none of them are innocent." Meanwhile, Blackburn advances through the train. He unlocks a door that had been jammed via an M1014. However, upon reaching the first corner, he is ambushed by a PLR insurgent with an AKS-74u. After a brief melee, Blackburn manages to take the enemy weapon and force the insurgent out onto the tracks, although losing the M1014 in the process.

Blackburn then encounters Solomon behind an unbreakable window. The insurgent leader primes a set of explosive charges, and then walks away, whereupon Blackburn climbs out of the train and jumps from one car to the next, narrowly escaping the subsequent explosion. Solomon fires at Blackburn who stumbles and nearly falls onto the train tracks. However, he recovers, and manages to climb onto the top of the train. As he slowly advances, he is attacked by several insurgents. Another explosion occurs on the car in front of Blackburn, allowing the marine to re-enter the train. After killing several more PLR insurgents, Blackburn reaches a car that seems empty apart from a single insurgent, who raises his hands. Solomon ambushes him, and demands to know if Blackburn is on his own.

The level is continued in the form of the final level.