Sector B of New Mombasa was one of the city's four primary sections, the others being Sector A, the City Centre, and the Docks. Sector B was located at the heart of the city's industrial zone, and many industrial buildings such as Tterrab Industries were located there. The highway New Mombasa 105 East led to the sector through the Mtangwe Underpass, a tunnel with its other entrance located at the end of the Mombasa Suspension Bridge. According to the sign on the Old Mombasa side of the New Mombasa bridge, Sector B is 1 km away from that part of the bridge.
In 2552, Sector B was one of the Covenant's main incursion points in the Battle of Mombasa during the Battle of Earth. They landed heavy armor, including Wraith tanks, Shadow transports, and Ghosts with air support from Phantoms and Banshees in the sector. UNSC Marines from the 405th Division were sent to the area as well, but were pinned down until help arrived from the reinforcements provided by the UNSC In Amber Clad, including John-117. A Scarab walker retreated there as well, having traveled down the NM 105 E to the city to get a clear line of sight at the New Mombasa Orbital Elevator.