From Halopedia, the Halo wiki
Operation: BUMRUSH was a UNSC attempt to infiltrate and force down the Prophet of Regret's flagship, Solemn Penance, during the Battle of Mombasa as part of the nascent Battle for Earth on October 20, 2552.
During the opening stages of the Battle for Earth, the Penance blew past UNSC defenses in orbit and set course for the African mega-city of New Mombasa, settling over the Uplift Nature Reserve and deploying massive numbers of ground infantry and heavy equipment with the intent to drive the UNSC out of the area to begin its excavation effort for the supposed Forerunner Ark. Realizing that they were at a tactical disadvantage, all Covenant forces eventually began retreating to Regret's carrier.
As the battle on the ground intensified, FLEETCOM issued an unexpected order: several vessels of the Fifth Fleet were to launch a force of ODSTs onto the carrier to breach its hull and force the ship down by gaining access to the interior.
At 1602 hours, Operation: BUMRUSH was greenlit and these vessels, among them the cruiser Say My Name, deployed their respective contingents of troopers into Earth's atmosphere above the city. At 1603 hours, one minute into the drop, the Penance suddenly initiated an in-atmosphere slipspace jump, creating a massive electromagnetic pulse that fried the safety and navigational systems of the troopers' drop pods, sending them all free-falling to near-certain death and effectively terminating the operation.
Alpha-Nine, having diverted their trajectory at the last minute, is the only squad known to survive the drop, albeit scattering its troopers across the city. After regrouping, Alpha-Nine was able to escape the city in a stolen Phantom before it was glassed. Regret, having entered Slipspace to escape the city, arrived at Halo Installation 05 about two weeks later, precipitating the Battle of Installation 05 and his eventual death at the hands of Spartan-II John-117. The ultimate fate of the Penance is unknown.
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