From Halopedia, the Halo wiki
Upon completing it on Normal, Heroic, or Legendary the player will unlock Assault achievement, worth 20 Gamerscore. If a player gets more than 15,000 points in the meta-game he or she will unlock the Askar achievement, worth 10 Gamerscore.
It begins with a UNSC Warthog convoy moving to Voi, its objective to punch through the Covenant anti-aircraft defenses that surround the supposed Ark and allow Lord Hood's small fleet to launch a direct strike against the Prophet of Truth's Dreadnought in hopes of killing Truth and stopping the firing of the Halo rings. UNSC Marine forces, led by John-117, fight through several pitched skirmishes through the industrial zone of Voi.
After breaking through the industrial area, John meets up with a group of approximately five Mongoose ATVs and commandeers one with a Marine riding 'pillion' using a rocket launcher. They immediately engage a squadron of Anti-Air Wraith tanks to secure a landing zone as Brute Choppers and Ghosts attack. Covenant forces are being continually reinforced by Phantoms. Hornets and Banshees fly above, vying for control of the skies. Although they manage to take the landing zone, the victory ends up being short-lived as a Scarab arrives to crush the UNSC forces. After John destroys the massive walker, remaining UNSC forces prepare to push into a Jiralhanae-controlled warehouse.
With reinforcements led by Thel 'Vadam along with the Voi Factory Workers, the Chief and his allies push onwards, engaging nearly a dozen Jiralhanae armed with spikers and brute shots, a pair of Mgalekgolo, and a Jiralhanae Chieftain wielding a Gravity Hammer. They finally press on to the anti-aircraft battery, engaging a small Covenant force defending it, including a Jiralhanae War Chieftain. Eventually, they succeeded in destroying the gun, enabling three UNSC frigates to attack Truth's ship. Unfortunately, the assault fails to damage Truth's ship. The artifact opens and activates a massive portal, which Truth and the rest of the Covenant fleet use to escape. Before the UNSC can figure out what to do next, a badly damaged Covenant cruiser enters Earth's orbit and crashes into a nearby factory. An even deadlier enemy has arrived...
Military Operations Urban Terrain.
A convoy of three Warthogs: two M831 TT Warthogs and one M12 Chaingun Warthog roll down a tunnel of Tsavo Highway, with the Chief riding shotgun in the LRV. (On co-op, Thel 'Vadam and N'tho 'Sraom ride shotgun on the TTs, but Usze 'Taham uses the turret of the Warthog the Master Chief is riding on).
The Warthogs emerge from the tunnel in a parking lot scattered with destroyed Warthog chassis and Marine and Unggoy corpses. The Warthogs roll to a halt as the Marines and Master Chief walk out, and the Marines form a perimeter outside the locked door. (On co-op, Thel 'Vadam and N'tho 'Sraom will also get off their warthogs, but Usze 'Taham will remain unless he chooses to get off.)
The Master Chief opens the door into an empty factory section, moves up a flight of stairs, and heads out onto a catwalk overlooking an area with a few Unggoy and Kig-Yar, who are listening to another of Truth's sermons.
The Chief opens fire, taking the Covenant by surprise.
The Chief finds the door controls on the upper level and activates them. The doors open and an M12 Warthog LRV and a squad of Marines enter.
The Marines wipe out any remaining Covenant troops in the immediate area. Three more Unggoy enter the room, but they too are killed.
The Chief heads back down to the ground floor, and opens a second set of doors, leading to a factory tunnel full of Jiralhanae, Kig-Yar, Unggoy and even a pair of Ghosts. Beyond that is another door leading outside to Lake Bed A. After cleaning out resistance in the tunnel, the UNSC forces open the next door, revealing a massive expanse with cruising Ghosts and a heavy Covenant garrison, along with an Anti-Air Wraith which fires at Hornets overhead.
The Chief can take a Ghost, the Warthog, or proceed outside on foot.
If the player stalls:
A team of Marines are forced to retreat from a small dock office in the center of the lake bed as a Phantom dropship drops Covenant troops directly on top of the structure. The Master Chief and accompanying Marines rendezvous with the displaced team and together they assault the dock office, clearing it of Covenant. The Ghosts attack the UNSC force, but are repelled. A Phantom drops extra Ghost reinforcements, but the Chief and company destroy these too. Another Phantom deploys a standard Wraith at the opposite end of the lake bed.
With most of the opposition destroyed, the Chief destroys the Anti-Aircraft Wraith.
A pair of Banshees swoops down to attack the UNSC forces. A friendly Hornet arrives and destroys the Banshees. The Chief and the remaining Marines cross the lake bed and neutralize the Wraith guarding the entrance to the factory. Another lance of Covenant attempt to stop the UNSC force, but fail.
If the player stalls:
If the player further stalls:
The Chief engages the Covenant.
The Chief goes upstairs and flanks the Covenant troops, forcing them out into the open where the mounted machine gun can cut them down. The Covenant soldiers are soon wiped out.
If the player brought the Warthog from the last section:
The Chief meets up with the Marines operating the mounted machine gun.
The Chief heads downstairs and opens a heavy door (or a Marine does it for him), giving him access to the next section of the factory.
A Phantom hovers overhead above a glass roof.
The glass roof shatters and a horde of Yanme'e descends. The Chief and the Marines stand their ground and fight off the swarm. The Phantom eventually leaves and any remaining Yanme'e flee. The Master Chief and Marines proceed into the next factory tunnel section.
At the end of the tunnel are four Mongoose vehicles, next to a rack of weapons. Marines rush to man the ATVs.
The Chief (or a Marine) opens the tunnel's door, leading outside to a neighboring lake bed.
The Chief takes a Mongoose (or any other vehicle of choice) and heads outside with other ATVs. A small squad of Marines has taken refuge on the boardwalk on the northern side of the lake bed. They are shortly engaged by a Covenant lance. Multiple Jiralhanae Choppers and Ghosts mill about in the center, guarding two more Anti-Air Wraiths. In the sky above, Banshees and Hornets are engaged in a fierce dogfight.
The ATVs quickly take out the first Anti-Air Wraith.
Enemy Phantoms deploy additional Ghosts onto the battlefield. The Marines on the northern boardwalk use a pair of mounted Missile Pods to support the Chief from a distance.
The Chief takes out the second Anti-Air Wraith. The ATVs, Hornets, and Missile Pods eventually clear the lake bed of remaining Covenant resistance. Pelicans arrive to deliver reinforcements.
Scarab. BFG. End of World.
There is the booming of the anti-aircraft emplacement in the distance, but also an ominous mechanical grinding noise.
The booms and grinding get louder.
A massive Scarab walker lumbers down from the roof of the factory onto the lake bed, and dust rises as its legs slam into the ground, destroying a Troop Transport Warthog in the process.
If the player waits around:
The Chief, Marines, ATVs, Hornets, and Missile Pod emplacements eventually take out one of the Scarab's joints, forcing it to lower itself and consume all power into getting back up again, deactivating its primary weapon in the process.
If the player wastes more time:
The Chief boards the Scarab.
On the upper deck of the Scarab, the Chief neutralizes several Jiralhanae, Kig-Yar and Unggoy trying to stop him.
If the player stays on the Scarab for a while:
The Chief goes to the rear of the Scarab, where he finds and destroys the power core.
The Chief jumps off the Scarab and runs for it. With a loud roar, the Scarab detonates violently in a blinding flash of light.
Alternatively, the Chief can use one of the missile pods to destroy the Scarab from a distance.
A Pelican lands and drops off Thel 'Vadam. A fresh squad of Marines lead 'Vadam and Master Chief to a locked door leading to the factory's warehouse.
The door opens up, leading to a dirty tin-walled section filled with wounded Marines and civilians lying on the floor. Several grim-faced Marines are standing behind sandbags, tending to the wounded and operating the sole UNSC field radio available.
Voices begin to play through the radio and are attentively monitored by a pair of Marines operating it.
There is a moderate pause within the radio conversation, before another starts between Commander Keyes and Lord Hood. This conversation foreshadows the very end of the level.
The Master Chief and Thel 'Vadam pass through a stained area of bolted tin plates until they reach the periphery of the warehouse, where a trio of Marines are pinned down under sandbags as spiker projectiles fly through the air. Farther forward is a steel bridge where a pair of Marines frantically open fire on Jiralhanae all around them with a mounted machine gun.
After the Jiralhanae between the sandbags and the bridge are killed by the UNSC forces, another group of Jiralhanae charges from the next section, chasing two Marines.
A surviving Jiralhanae from the previous wave tries to warn the charging Jiralhanae of the impending doom but is too late.
They then run towards the bridge and a Marine fires the bridge-mounted turret.
After the last wave of charging Jiralhanae is killed, the Master Chief, 'Vadam, and the surviving Marines make their way into the next section, where behind a mass of stacked crates a Jiralhanae violently throttles a construction worker. Three other workers armed with Pistols flee from the Jiralhanae and his pack. The throttling Jiralhanae roars out.
The Chief and his allies kill the Jiralhanae.
The next section is littered with civilian corpses, while a few live Factory Workers cower in the corner. A door leading to the outside of the factory is nearby. The door opens up, and a group of four construction workers runs in. However, they are cut down by two massive green beams of energy blowing up the fusion cores next to the workers.
A pair of Mgalekgolo charge in over the worker corpses and after the Master Chief, Thel 'Vadam, and the awaiting Marines. The cowering workers get up and are relieved to see fellow humans.
Their celebration is cut short when they see the Mgalekgolo and retreat behind the approaching Marine forces.
If the fight continues for a while:
After a firefight, the Chief and company manage to take out the Mgalekgolo pair. The Marines, Master Chief, and Thel 'Vadam run through the open door to a series of low-roofed buildings where a Jiralhanae Chieftain awaits with his Bodyguards and several Unggoy. The Prophet of Truth sermonizes from a holographic pedestal behind them.
After the Unggoy are wiped out, the Chieftain retreats with his Bodyguards back to the pedestal, where a larger force of Jiralhanae, Kig-Yar and Unggoy wait. After a protracted struggle, the assault force finally defeats the Covenant troops and continues on ahead. Truth continues preaching.
The Chief, 'Vadam, and the surviving Marines and civilians move around the remaining buildings and reach the hill where the massive anti-aircraft emplacement stands. Weapons can be found among the Marine corpses lying behind sandbags at the base of the hill. The Covenant AA gun opens fire on a surging UNSC Longsword and scores a direct hit on its engines. The damaged craft plunges into the cliffs below.
The Chief, 'Vadam, and the remaining Marines and civilians push up the hill. Unggoy tentatively run down the slope to face the onrushing UNSC forces. The Chief eliminates them and presses forward. Mid-way up the hill, he encounters a Jiralhanae War Chieftain wielding a fuel rod gun. The War Chieftain is backed up by his Jiralhanae Captains and Bodyguards, as well as an Unggoy Heavy manning a plasma turret, and Unggoy and Kig-Yar infantry. Numerous Banshees patrol the sky above (on higher difficulties, they will occasionally swoop down and strafe the player).
Eventually, the Chief and his allies take down all the Covenant ground defenders.
If the player delays:
If the player still delays:
The anti-aircraft emplacement's lower section opens to reveal a white sphere. Steam vents as the panel continually opens. The Master Chief destroys the sphere.
The AA Gun explodes in the background, sending the upper section flying down the cliff. The Master Chief joins 'Vadam on the cliff side of the crater. They look up as multiple squadrons of Longswords streak overhead, followed by three UNSC frigates, including the UNSC Forward Unto Dawn, Lord Hood's flagship. The Covenant fleet hovers before them, with the Forerunner Dreadnought positioned below at the center of the artifact.
The frigates engage the Forerunner Dreadnought. Their Magnetic Accelerator Cannons discharge in volleys, and explosions coat the Dreadnought's surface, but the ship remains unscathed. The Forerunner structure begins to open like a starfish. The Dreadnought is lowered into the structure, an energy beam being focused through it. The storm intensifies. A powerful wind knocks John and 'Vadam backward. The beam of light grows thicker and expands, sending out a shockwave. Everything blacks out.
Scene fades in on the Chief, dazed and kneeling on the ground. He gets back to his feet and stares up. A large glowing sphere of blue light, centered by pitch darkness, hovers in the sky above the artifact. The large fins of the artifact focus energy on the sphere. UNSC and Covenant ships alike drift in the air, disorganized.
Truth's Dreadnought rises from the ground and approaches the sphere.
Thel 'Vadam roars angrily as the Forerunner Dreadnought disappears into the sphere. The rest of the Covenant fleet follows.
A damaged Covenant battlecruiser emerges from Slipspace to the east of Voi, and hurtles just over the Chief and 'Vadam. It is smoking with rancid fumes and its underside is covered in a sinister, fleshy growth. The ship soon loses altitude and crashes out of sight. There is a flash of light and a deep rumbling is heard, followed by silence. The sky darkens as smog rises, veiling the sun. An omen of ancient evil is in the air.
Scene cuts to a close up of John-117.
Fades to black.