Fort Santa Monica is a U.S. military base located at the Santa Monica Pier in Los Angeles, California.
Logan Walker, David "Hesh" Walker, Riley and Team Two scout near the Liberty Wall for any sign of Federation activity after they had overrun Dallas last night. Once they regrouped with the allied reconnaissance team, they encountered another Federation recon team who executed a group of civilians. Following this, they helped US forces to defend the Wall. After the area is cleared, the Walker brothers, Riley and a soldier traveled in an MATV to the base, where they meet up with their dad Elias T. Walker, who debriefs and give them of their next mission.
After the Walker brothers secured an enemy helicopter and took off from Firebase Charlie in San Diego, their father called them to return to Fort Santa Monica quickly because the Federation launched an amphibious assault on the base with a large force of landing units. They helped the allied forces there to launch an counterattack on the Federation forces. Logan uses a mounted machine gun to stop the invaders on the beach until the building was destroyed by an Mi-24 Hind. Logan uses A-10 Thunderbolt II drones to provide close air support until the drones and their control tower are destroyed. Following this, allied forces are falling back from the beach. The Walker brothers headed to the damaged forward command center to find their dad but a Federation soldier ambushes and stabs Logan. He is saved by David, who helps treat his wounds. Then, part of the roof breaks and two men, hanging from a helicopter above, grab Logan and David (and somehow, Riley as well). Aboard the helicopter is Merrick and Keegan, the two Ghosts from No Man's Land. Another Ghost, who hasn't been seen before, takes off his mask and is revealed to be Elias to David and Logan's most likely surprise.
It is later revealed in the game (if the player checks out the Rorke file found in the mission All or Nothing) that the U.S. military had successfully defended the base because the U.S. mobilized all its remaining forces from the base.