Battle of Alpha Base
On September 19, 2552, human forces of the UNSC Pillar of Autumn landed on Installation 04 and proceeded to take over the Forerunner structures on a butte, later referred to by the humans as Alpha Base. The humans began to repeatedly raid Covenant deployments across the ring, with Lieutenant Melissa McKay leading a raid on the downed Autumn to retrieve vehicles, munitions and supplies for the UNSC base. The raid was a success, arming Alpha Base with a fleet of M12 and M12B Warthogs, four M808B Scorpion tanks and even two M910 Rampart 50mm autocannons. Additionally, a UNSC attack on the Truth and Reconciliation allowed Lieutenant Dalu to salvage several Type-29 and Type-26 Covenant Shade turrets to bolster the defenses of the operating base.
During the attack on the Pillar of Autumn, Sangheili Field Master Noga 'Putumee led a Covenant force in attempting to halt the UNSC armored column, but ultimately failed in this task. The series of repeated blows to the Covenant prompted the Council of Masters to grant Zuka 'Zamamee permission to lead an attack on Alpha Base.
His Unggoy assistant Yayap was left to be found by the UNSC forces, and transported to Alpha Base. The Unggoy was to activate a signaling device once he spotted John-117, alerting the Covenant to his presence so he could be eliminated. However, by the time the battle had started, the Master Chief had departed the base.
By 0236 hours on September 21, the final mission arrived back at Alpha Base for the night, with no more flights scheduled. The Battle for Alpha Base began with a distress relay call from the Pelican dropship Charlie 217. This Pelican had been listed as MIA, and so was allowed to land on one of the pads at Alpha Base, although a Marine reaction force was put on standby. The Pelican was piloted by Lieutenant Rick Hale, a Covenant prisoner. As soon as the Pelican was given permission to land, the lieutenant was strangled to death by Zuka 'Zamamee using an energy garrote. Wellsley, the Alpha Base AI, detected six additional heat signatures behind the Pelican which he recognized as Spirit dropships inbound at 350 kph. Though he was unable to prevent Charlie 217 from landing, he was able to warn his superiors to mount a response.
Thirty heavily armed Stealth Sangheili disembarked from the dropship and attacked every Marine in sight. Despite being caught mostly unaware, the UNSC forces rallied and fought back, flooding the landing pad with fuel and setting it aflame with a grenade, killing a number of the attackers and destroying the Covenant-captured Pelican. An explosion around this time shook the entire base, and alerted the remaining troops to the battle. The base's UH-144 Falcon complement began to fend off the inbound Covenant dropships and Banshees, while Fireteam Raven began to defend the base from encroaching forces. Several Spirits began to deploy their forces of Sangheili, Unggoy and Yanme'e inside the base, led by an Ultra. Banshee air strikes eliminated several Marines and a Pelican dropship, and Raven were ordered to get to the Shade turrets to help fend off aircraft. On the way they encountered more resistance, eventually using M41 SPNKRs to take down a Type-52 Phantom and several Type-32 Ghosts. A Spirit dropship would proceed to deploy two Mgalekgolo, though Raven would also take the Hunters down before finally mounting the Shades.
The ODST squad proceeded to take down several waves of Phantoms and Banshees before a new threat appeared - the Type-56 Lich Upright Chalice. The large shuttle would hover near the base, allowing its infantry to fire down onto the mesa, though the majority of the onboard complement would be killed by return fire thanks to Fireteam Raven, including a Sangheili Zealot. The fireteam dismounted and were ordered to get to the base's landing pad, as they were needed elsewhere on the ring. They engaged more energy sword wielding ultras, Hunters and Suicide Unggoy before finally reaching their Falcon and extracting off the Mesa as the battle continued.
Wellsley utilized a 50mm Autocannon and shot down one of the Spirits before they could get out of range. The 5 remaining Covenant ships touched down on the mesa and unloaded the main attack force, as well as Field Master Noga 'Putumee. Meanwhile, Zuka 'Zamamee and five of the remaining Stealth Sangheili descended into the underground level of the base, slaughtering all the humans that they came across. Finally, they entered the Control Room and massacred technicians Cho, Pauley, and Murphy. However, they were seen by Wellsley, who promptly warned Silva. Soon, six teams of three Marines were sent out to halt the Stealth Sangheili; to counter the active camouflage, the Marines had special equipment which allowed them to read the thermal heat given off by the active camo. The Sangheili questioned everyone they came across in an attempt to learn the Master Chief's whereabouts. Eventually they came across Yayap and three other Unggoy in a prison cell. The Unggoy convinced Zuka that the Spartan was guarding a group of captured Banshees on the other side of the base, and led the group toward there. A three-man Marine fireteam surprised them, killing the five Stealth Sangheili and the three Unggoy before being taken out by a plasma grenade from Yayap. Upon reaching the Banshees, Yayap pointed a plasma pistol at 'Zamamee's head to get Zuka to fly them both to safety.
Meanwhile, McKay was tasked with halting the Covenant forces on the plateau. The primary Covenant attack force had been thoroughly destroyed. First, the snipers attempted to kill the majority of the enemy ground forces. 'Putumee, unable to land on the pads as originally planned, alternatively landed on the area up-spin of the Forerunner complex. Despite having the remaining Spirit dropships strafing the Marine defenders, they were caught unaware by the pair of entrenched M808B Scorpions and prepared defenses on the plateau. Not only did the Scorpions obliterate the majority of the Covenant forces, but also deprived the Covenant forces of their leadership when 'Putumee was killed. However, the assault moved onward, albeit slowly, as the lower-ranked Sangheili assumed command and attempted to rally the troops without much success. Soon, the strafing Spirits picked up the few surviving Covenant troops and retreated.
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