Full list of all 58 Halo Wars achievements worth 1,200 gamerscore. It takes around 80-100 hours to unlock all of the achievements in the base game on Xbox 360.
The base game contains 50 achievements worth 1,000 Gamerscore, and there are 2 DLC packs containing 8 achievements worth 200 Gamerscore.
Obtained the General Rank on Xbox LIVE
Finished all missions under Par Time on Heroic difficulty
Completed the Campaign on Legendary Difficulty
Completed the Campaign on Heroic Difficulty
Completed entire Campaign in Co-op Mode
100% Completion
Got 20,000 points in any Skirmish Game
Got a Gold Medal with all Debuff Skulls Active
Mission 7: Did not destroy any Power Node
Won a Heroic Skirmish Game against the AI in under 10 minutes
Got a winning High Score with 10 or less Squads against the Heroic AI
Obtained the Lieutenant Rank on Xbox LIVE
Won a game on every Skirmish Map
Unlocked All Timeline Events
Got a Gold Medal on every Campaign Mission
Collected all Skulls
Mission 14: Didn't claim an extra base
Mission 13: Destroyed 25 units with the Scarab
Mission 12: Repaired the Power Core in less than 4 minutes
Obtained a Lifetime Campaign Score over 1,000,000
Mission 10: Disrupted all Tractor Beams
Mission 6: Successfully protected every Rhino
Mission 5: Jacked 6 Covenant Vehicles
Mission 4: Saved Adam
Mission 2: Destroyed every Methane Tank
Played Halo Wars for at least 24 Total Hours
Mission 1: Rammed 50 Grunts with Warthogs
Won a Skirmish Game with every Leader
Won a Skirmish Game with Dual Scarabs
Won a game in every Skirmish Game Mode
Used one of the 6 Major Leader Powers to destroy an enemy's last unit
Unlocked 20 Timeline Events
Won a 3v3 Skirmish game with 2 AI Allies
Won and had the Highest Score in a Matchmade Skirmish Game on Xbox LIVE
Won a Matchmade Skirmish Game on Xbox LIVE
Completed Act IV on any difficulty
Mission 15: Opened the Doors in order
Mission 8: Used Elephants to train 100 Infantry
Completed Act III on any difficulty
Mission 11: Saved all the Airlocks
Mission 9: Put every Colony in Hibernation Mode at the same time
Completed Act II on any difficulty
Obtained the Recruit Rank on Xbox LIVE
Completed Act I on any difficulty
Mission 3: Killed at least 5 Covenant Units with the Bridge
Collected your first Skull
Completed any Campaign Mission in Co-op Mode
Improved your Score in any Campaign Mission
Got a Gold Medal on any mission
Completed Mission 1 on any difficulty
Scored the winning point in a game of Keepaway against Legendary AIs.
Got a Scarab during a Reinforcement game.
Won and never trailed in a Tug of War game.
Gained at least 15 population from a single wave in a Reinforcement game.
Hot dropped 50 squads to your Covenant Leader in a single game on Barrens.
Finished with 5000 net resources tributed to your teammates on Memorial Basin except in Deathmatch.
Killed 20 enemy squads with a continuous Covenant Leader Power on Memorial Basin.
Disrupted 5 active Leader Powers in a single game on Blood River.