Battle for the Truth and Reconciliation

Numerous raids took place over Installation 04 as the Marines of the boarded the damaged, the Truth and Reconciliation.

First raid - rescuing the Captain
Shortly after the evacuation from the Pillar of Autumn, Captain Jacob Keyes was captured by Covenant forces and taken to the Truth and Reconciliation, where he was promptly imprisoned in one of its detention centers.

After word got out of his capture when AI Cortana hacked into the Covenant battle network, a force of Orbital Drop Shock Troopers dressed in urban-warfare fatigue assisted Master Chief Petty Officer John-117; a SPARTAN-II, in the initial boarding of the ship. Using faked signals and an opening in the Covenant ship's sensor network to their advantage, the UNSC forces inserted to a nearby plateau and took out the ground forces guarding the ship's gravity lift. Entering the ship, the group was attacked by numerous waves of the ship's military complement.

Leaving the ODSTs in the ship's control center, the Master Chief proceeded to hunt for Captain Keyes solo. Eventually finding him and several imprisoned marines, the group headed back to the control room. However, in the time it took John to find Keyes and head back, the ODSTs guarding the rally point had been slaughtered by Energy Sword-wielding zealots.

After Covenant Banshees located the Pelican Echo 419, which was giving support for the mission, Keyes changed the objective. Rather than waiting for Echo 419 to return safely, the group went to one of the Truth and Reconciliation's hangar bays, where they stole a Type-25 Troop Carrier.

Second raid - return to the Captain
During the UNSC raid on the Flood containment facility, Captain Keyes was infected by the flood super cell via an Infection Form. Initially becoming a Combat form, his tactical knowledge was considered important to the parasitic organisms, and he was converted into a Proto-Gravemind along with a Sangheili officer after the Flood began to take over the Truth and Reconciliation on 21 September.

In order to destroy the Pillar of Autumn and sterilize the Flood outbreak, John-117 and AI Cortana required Captain Keyes' command neural interface, which contained the code for the Autumn's auto-destruct system. Initially arriving just outside of the control room, John had to escape from a seemingly infinite number of Flood attackers in a locked-down part of the ship by jumping out of it; a pool of the ship's reactor coolant broke his otherwise fatal fall. Returning up the gravity lift, John searched for an open door for the control room. The Captain managed to hold onto his humanity long enough to communicate with John via a UNSC comm system, confirming his survival. However, his orders to leave him and escape were taken less seriously and thought of by Cortana as evidence of being mentally disturbed.

Finally reaching the center, they found that they were too late: Keyes had fully merged with the calcium blob and became a part of the Proto-Gravemind. With no other option, John punched through the former Captain's head and took out the neural interface. The two commandeered a Banshee flown into the hangar by Covenant Special Operations personnel and headed straight for the Pillar of Autumn's crash site.

Third raid - capture
Not long after the Master Chief's departure, he alerted Alpha Base of his intent to destroy the ringworld. The relatively large force of Marines; ODSTs and crewmen deemed too important to be put into cryonic suspension -and thus were not ejected into space, were evacuated on the remaining few Pelican dropships as their home since the 19th was finally abandoned.

Arriving onboard via the hangar bays, the Covenant and Flood had managed to almost kill each other off. With only a few remaining enemies, the UNSC forces managed to quickly gain control over essential systems; notably the control room. They even managed to capture the Prophet of Stewardship who was aboard the vessel at the time. The Prophet sent an emergency rescue request to the fleet, but this request was denied by Supreme Commander Thel 'Vadamee, as the ring's destruction was imminent and the fleet proceeded to move into cover behind Threshold.

The mission commander; Major Antonio Silva, planned to take the ship into orbit and rendezvous with the Master Chief before jumping to Earth. His lieutenant however, disagreed with him. Realizing that the Flood's parasitic nature was too dangerous to let it spread, along with the potential discovery of Earth by the Covenant were the ship to enter UNSC space, she threw an M9 grenade onto an important piece of circuitry. The grenade's detonation severed the link between the command centre and engineering, deactivating the ship's repulsor engines in-atmosphere. The Truth and Reconciliation collapsed onto the plateau it was resting on, resulting in a spectacular explosion of fire and plasma.