Landing on Installation 04

On September 19, 2552, forces evacuating from the landed on Installation 04, amidst the ship's crash-landing. In the following hours, UNSC forces would regroup at a site later named "Alpha Base" and begin conducting strike operations across the ring.

Prelude
Following the arrival of the Pillar of Autumn in the Soell system, Covenant forces of the Fleet of Particular Justice moved to engage the ship. Under orders from the Minor Prophet of Stewardship, the fleet was forbidden from firing their ship-borne weaponry for fear of damaging Installation 04, and instead launched waves of boarding craft to try and flush the humans out. Nonetheless, Thel 'Vadamee eventually ignored this request and began to fire on the human cruiser anyway. The battle in space would prompt Captain Jacob Keyes to initiate Article 2 of the Cole Protocol, ordering a general evacuation of the ship. Most of the crew would evacuate by SKT-9 Bumblebee lifeboats, while the ship's ODST complement under Major Antonio Silva would deploy in their SOEIV drop pods.

Alpha Base
The Orbital Drop Shock Trooper complement of the Pillar of Autumn would depart the vessel aboard their drop pods, equipped with two weeks of supplies each. Consistent with UNSC Insertion Protocols, Major Silva's drop pod would enter the atmosphere of the ring first. Reasons for this were twofold; aside from the held belief that officers should lead, not follow, the practicalities of organising an invasion force meant needing to sort, organise and gather the available troops in the "golden hour" - the period of time in which the actions of the troops would most determine the success or failure of the mission. Silva's drop pod was appropriately configured with a Class-C AI - Wellsley - and high-powered imaging gear. Wellsley began to feed Silva reports of potential areas in which the ODSTs could hole up and defend, with one mesa dubbed "HS2604" serving nicely. The mesa was later named "Alpha Base", though first it had to be taken from the Covenant occupiers.

The ODSTs landed in an area roughly three kilometres in diameter, with many of the pods smashing into cliffs, landing in lakes and one rolling into a ravine. However, the remainder were able to make their way towards Silva's position. Lieutenant Melissa McKay landed only half a kilometre away from Silva, and was briefed on the future-base by Silva. The base was heavily fortified, meaning that it would need to be taken by ground and air forces. Luckily, several Pelican pilots had managed to land their craft roughly ten kilometres to the north, and they would be used to launch air strikes and ferry troops from above while McKay's roughly 130-strong B company would assault from the ground. McKay's company spent the next night marching to the mesa, eventually ending up at the base. Thankfully, the Covenant had been unprepared for the arrival of a human cruiser and its troops, and all that blocked the troops was a hastily-constructed barricade.

While B company prepared to assault the mesa, C company was designated to begin their march towards the Pelicans for aerial insertion and A and D company - under Silva - rested for the night in preparation for the day ahead. The companies camped out on a low rise without much cover, so instead tried to build up fortifications as much as they could while they slept. Wireless sensors monitored by Wellsley were placed two hundred meters around the camp and three-man fireteams took up position one hundred and fifty meters out, with a rapid response team established to support them. Trenches and dirt barricades were dug out and a flat area for Pelicans to land was cleared. Around the time McKay's team began climbing the mesa, Wellsley reported that a Covenant response force was inbound to Silva's company, consisting of roughly one hundred Ghosts, for Silva's two hundred infantry. Silva ordered the troops to form an infantry square, with ammunition moved down into the trenches alongside support weapons, with rocket launchers located halfway up the rise and snipers on the top of the landing pad. With guns facing out every direction, the formation would be difficult to break. The ODSTs were surprised at being ordered to use such an archaic tactic, but complied nonetheless, and once ordered to fire, their armor-piercing rounds ripped through the light scout vehicles easily. The skittish nature of the vehicles caused many pilots to crash into each other, though eventually a gold-clad elite managed to organise the raiding force into circling the camp counter-clockwise to reduce collisions.

The Ghosts began to focus their fire on one of the pits, beginning to kill the humans stationed there and slowly weakening one quarter of the camp defenses, prompting Silva to send a squad to reinforce and ordering his snipers to concentrate on eliminating the leader. The rocket-wielding heavy troops began to fire in volleys to make sure there wasn't a downtime between firing, and eventually the mangled wreckage began to provide cover for the humans. Banshees were sent in after the Ghosts, though the four were easily repelled by the rocket launchers. After losing more than half their number, the Ghosts retreated, though the battle had resulted in twenty-three ODST casualties, six serious injuries and ten wounded personnel. By this time, McKay's company had engaged the enemy at the mesa, and Wellsley ordered the Pelicans to begin their attack.

The Pelicans utilised their 70mm chin-mounted guns to cut down Covenant troops and Shade turrets before dropping fifteen troops onto the mesa's landing areas each, with each dropship being ordered to return to their initial base and collect more troops for ferrying. Within minutes of the air attack, Covenant resistance in the base began to crumble. On her path up the mesa, McKay noticed a side door the Covenant had been defending, and ordered a rocket launcher be fired into the structure to clear out the inhabitants. By the time McKay's company made their way up the gravity lift to the surface, Silva and Wellsley were already on the landing pad and waiting - there had been several UNSC casualties but even more Covenant, and the rest of the battalion would be arriving within the hour.

John-117 and the crew
Many of the lifeboats deployed from the Autumn ended up scattered across the surface of the ringworld. Due to an airbrake failure, lifeboat Lima Foxtrot Alpha 43 - carrying Spartan John-117 and AI Cortana - crashed on the edge of a cliff, killing all on-board personnel except for the aforementioned Spartan. The Spartan emerged from the pod and took cover in the nearby hills as Covenant Banshees and Spirit dropships began to converge on the crash site to hunt down any survivors. The Spartan engaged Covenant light infantry forces on the ground before eventually hearing the sound of UNSC weapons fire in the distance. Moving towards the sound, he found a Forerunner structure held by several marines and naval crewmen, besieged by Covenant troops.

Other survivor groups
Several groups of UNSC personnel landed on the surface of Installation 04 that went unaccounted for later in the battle. Fireteam Raven, an ODST fireteam, landed on the ring in time to view the Pillar of Autumn crash. Guided by Wellsley via mobile uplink, Raven would eventually meet up with Lieutenant McKay and her company during the midst of the later Raid on the Pillar of Autumn, twenty-eight hours later. Another group of survivors would land near a large Forerunner complex similar in appearance to Alpha Base, though deep in the forest. These survivors would make a staging area, though a Covenant assault later in the conflict would wipe out the encampment.

Another group of ODSTs would land near a similar cliffside beam emitter as the one encountered by the Master Chief, and hold off Covenant attacks there.

Pelican pilot Rick Hale would suffer several issues with his dropship upon leaving the Pillar of Autumn, and would eventually put down in the remote regions of the ring to work on repairs. He would later be captured by the Covenant, and eventually forced at gunpoint to fly a Pelican loaded with Special Operations Sangheili onto the landing pads of Alpha Base, kickstarting the Battle of Alpha Base two days later. An Unidentified private of the 79th Infantry Battalion would later send a report through the transmitter of lifepod Lima Foxtrot Alpha 19 reporting that his unit had been devoured by the Flood following the parasite's outbreak later in the conflict. It is unknown if this marine, and his unit, were able to link up with the UNSC forces of Alpha Base. Several other personnel including Elias Haverson, Marvin Mobuto and Thomas Chang would land on the installation, and have thus far gone unconfirmed as to whether they were able to link up with the forces of Alpha Base.

Capturing the command crew
During the space battle, Sangheili Isna 'Nosolee was deployed onto the Pillar of Autumn as an Ossoona, or "Eye of the Prophets". The Sangheili was tasked with three objectives; capturing the ship's AI, command crew and recording anything he saw. Deeming the AI to be destroyed or removed from the ship, the elite began to find his way to the ship's bridge. Once the bridge crew found their way to their designated escape pod, the elite boarded, but the shimmer of his active camoflage gave him away and he was shot by Captain Keyes. The rest of the ride down to Halo's surface was uneventful, thanks to the flight skills of the pilot William Lovell. Once landed, the crew began to strip the lifeboat and dump the elite's body in a crevice, though it wasn't long until a sonic boom signalled the arrival of the Pillar of Autumn in the ringworld's atmosphere. The bridge crew began to climb up a nearby hill, intending to hide out in a cave until such a time as support could rescue them.

However, it wasn't long until the Covenant got wind of the landing site of the bridge crew. The lifeboat was quickly found, and 'Nosolee's body not lang after. From there, Covenant command was notified and it didn't take long for it to be determined that 'Nosolee wouldn't risk his life unless there was something of importance within the shuttle. From there, the Covenant began to search the region for the human commander, but there was only one problem; the hillside terrain made landing troops difficult, and it was still important to ascertain which human 'Nosolee had been seeking. Because of this, the Covenant began to deploy Banshee air recon, but were still at a disadvantage due to their strict orders to take the humans alive. Nonetheless, the tightening Covenant net proved difficult for the humans, who were constantly harassed at every turn, with Corporal Wilkins' marines managing to barely hold off the aliens. As the day went on, Ensign Ellen Dowski began to crack, beginning to complain and eventually beginning to suggest turning themselves over to the Covenant - reasoning that they could have been killed by plasmafire or bombs at any point, yet they were alive. Unable to charge the junior officer with insubordination, Keyes instead allowed Dowski to surrender, though ordered her stripped of weapon, supplies and tied up to make sure she couldn't follow the rest of the group.

Eventually, a Covenant dropship landed several Sangheili troops a kilometre to the south, prompting the party to once again set off. As they set off, the Sangheili Ado 'Mortumee noticed on his heat signature tracking that one of the dots on his screen was staying behind. Dowski was eventually picked up by the Covenant - alive, and assisted the Covenant in locating the rest of the command crew. For the next three hours, the party would continue to evade the Covenant, but eventually made their way into a box canyon with no retreat. As a Spirit began to descend into the canyon, Dowski's voice on the speakers informed the command team of this fact, and that there was nowhere to go. Eventually, Dowski jumped out of the dropship followed by a team of Sangheili, whereupon she identified Keyes as the leader of the group. The elites proceeded to execute the remaining crew, much to Dowski's horror, before executing her with her own pistol. They lifted Captain Keyes into the dropship and took him away to the brigs of the Truth and Reconciliation.

List of appearances

 * Halo: Combat Evolved
 * ''Halo: The Flood
 * Halo: Reach
 * Anniversary Map Pack
 * Halo: Combat Evolved Anniversary
 * Halo Mythos: A Guide to the Story of Halo
 * Halo: Fireteam Raven