This was where the Covenant would eventually begin their excavation for the Forerunner structure under the region. The slipspace rupture also created a large crater to the mainland, north of Mombasa Island. Although the whole of Mombasa Island was consumed by the explosion, only some buildings close to the slipspace vortex were sucked through. The ensuing shockwave and EMP engulfed the whole city, causing heavy damage to its digital infrastructure, and scattering the ODSTs' drop pods around the city at least the six members of Buck's squad survived landing. While the ODSTs were on their way down, Solemn Penance jumped into slipspace, with the In Amber Clad and 4 other ships in pursuit. Meanwhile, in orbit, an ODST task force was preparing to hot-drop onto the carrier. At this point, the Covenant troops were retreating back into the Solemn Penance, which was preparing to leave. After destroying the Scarab, the Chief returned to the UNSC In Amber Clad. After a series of quick battles in a public park and the city streets, the Chief boarded and destroyed a Covenant Scarab as it passed through the city's artificial canals. After fighting through the maze-like streets of the mainland, the Master Chief crossed the empty beach below the seawall and then entered the highway system and the bridge to New Mombasa. Later that day, Master Chief Petty Officer John-117 was deployed into Old Mombasa to assist UNSC forces to liberate the city from the Covenant. The rainy streets of New Mombasa, reduced to a ghost town.

It was also important as a port city, connecting East Africa to the Indian Ocean. During this era, Mombasa became a tourist destination, boasting numerous resorts and clean, white beaches. The city became part of the independent nation of Kenya in the 20th century. This violent history led to its Swahili nickname 'Kisiwa Cha Mvita', or 'Island of War'. Mombasa had always been an important port of the Indian Ocean trade routes and was captured and recaptured countless times by a variety of powers including Portugal, the United Kingdom, and various Arab forces.

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