Halo 3/Walkthrough

Sierra 117

 * Objectives: Destroy Covenant Loyalist encampments and find the UNSC Base and Find Johnson's Crashed Pelican .and save jonhson

Crow's Nest

 * Objectives: Defend the Base from incoming Covenant troops and escape the base.

Tsavo Highway

 * Objectives: Reach the Ark

The Storm

 * Objectives: Destroy Covenant anti-air wraiths, Destroy pursuing Scarab walker, and Destroy Covenant Loyalist anti-air emplacement

Floodgate

 * Objectives:  Stop the Flood Infestation and find Cortana

The Ark

 * Objectives: Take out the Brute's base on Installation 00

The Covenant

 * Objectives: Kill the Prophet of Truth

Cortana

 * Objectives: Save Cortana

Halo

 * Objectives: Activate the Ring

Achievements
Landfall (20 points): Finish the first mission of the Campaign on Normal, Heroic, or Legendary. Holdout (20 points) : Finish the second mission of the Campaign on Normal, Heroic, or Legendary. The Road (20 points) : Finish the third mission of the Campaign on Normal, Heroic, or Legendary. Assault (30 points) : Finish the fourth mission of the Campaign on Normal, Heroic, or Legendary. Cleansing (30 points) : Finish the fifth mission of the Campaign on Normal, Heroic, or Legendary. Refuge (30 points) : Finish the sixth mission of the Campaign on Normal, Heroic, or Legendary. Last Stand (40 points) : Finish the seventh mission of the Campaign on Normal, Heroic, or Legendary. The Key (40 points) : Finish the eighth mission of the Campaign on Normal, Heroic, or Legendary. Return (50 points) : Finish the final mission of the Campaign on Normal, Heroic, or Legendary. Campaign Complete: Normal (125 points) : Finish the Campaign on Normal. Campaign Complete: Heroic (125 points) : Finish the Campaign on Heroic (unlocks achievement for Normal, if not earned). Campaign Complete: Legendary (125 points) : Finish the Campaign on Legendary (unlocks achievements for Normal and Heroic, if not earned). Iron (10 points) : Find and claim this skull when playing on Normal, Heroic or Legendary difficulty. Black Eye (10 points) : Find and claim this skull when playing on Normal, Heroic or Legendary difficulty. Tough Luck (10 points) : Find and claim this skull when playing on Normal, Heroic or Legendary difficulty. Catch (10 points) : Find and claim this skull when playing on Normal, Heroic or Legendary difficulty. Fog (10 points) : Find and claim this skull when playing on Normal, Heroic or Legendary difficulty. Famine (10 points) : Find and claim this skull when playing on Normal, Heroic or Legendary difficulty. Thunderstorm (10 points) : Find and claim this skull when playing on Normal, Heroic or Legendary difficulty. Tilt (10 points) : Find and claim this skull when playing on Normal, Heroic or Legendary difficulty. Mythic (10 points) : Find and claim this skull when playing on Normal, Heroic or Legendary difficulty. Graduate (10 points) : Earn 5 EXP or finish 10 games to complete the requirements for basic training (Online). UNSC Spartan (15 points) : Earn your Sergeant rating to be recognized as a true Spartan (Online). Spartan Officer (25 points) : Advance to the Spartan Officer ranks (Online). Two for One (5 points) : Score a Double Kill with a single spartan laser shot in a ranked free for all playlist (Online). Too Close to the Sun (5 points) : Destroy an enemy banshee with the spartan laser or missile pod in a ranked playlist or in campaign. Triple Kill (5 points) : Kill 3 enemies within 4 seconds of one another in a ranked free for all playlist (Online). Overkill (5 points) : Kill 4 enemies within 4 seconds of one another in a ranked free for all playlist (Online). Lee R Wilson Memorial (5 points) : Score 5 grenade sticks in any ranked free for all playlist (Online). We’re in for some Chop (5 points) : Destroy an enemy vehicle with equipment in a ranked playlist or in campaign. Killing Frenzy (5 points) : Kill 10 enemies without dying in any ranked free for all playlist (Online). Steppin' Razor (5 points) : Score a Triple Kill with the sword in a ranked free for all playlist (Online). Mongoose Mowdown (5 points) : Splatter an enemy with the mongoose in a ranked free for all playlist (Online). Up Close and Personal (5 points) : Kill 5 enemies by melee or assassination in a ranked free for all playlist (Online). Fear the Pink Mist (5 points) : Kill 5 enemies with the needler in a ranked free for all playlist or in campaign. Headshot Honcho (5 points) : Kill 10 enemies with headshots in a ranked free for all playlist or in campaign. Used Car Salesman (5 points) : Destroy a vehicle that has three enemies in it in a ranked playlist or in campaign. Marathon Man (40 points) : Locate and access all Terminals in the Campaign. MVP (5 points) : Earn the MVP in any ranked playlist (Online). Maybe Next Time Buddy (5 points) : Board the same vehicle within 10 seconds after being boarded in any free for all playlist (Online). Guerilla (10 points) : Score over 15,000 points in the Campaign meta-game on the first mission. Demon (10 points) : Score over 15,000 points in the Campaign meta-game on the second mission. Cavalier (10 points) : Score over 15,000 points in the Campaign meta-game on the third mission. Askar (10 points) : Score over 15,000 points in the Campaign meta-game on the fourth mission.

Exterminator (10 points) : Score over 15,000 points in the Campaign meta-game on the fifth mission. Ranger (10 points) : Score over 50,000 points in the Campaign meta-game on the sixth mission. Vanguard (10 points) : Score over 50,000 points in the Campaign meta-game on the seventh mission. Orpheus (10 points) : Score over 15,000 points in the Campaign meta-game on the eighth mission. Reclaimer (10 points) : Score over 15,000 points in the Campaign meta-game on the final mission.