There's not actually any cheat codes available for Halo Wars, from what I can see. I think what you're seeing in the video is a strategy, not a cheat. From the video's description: "Effortlessly complete Mission 7: Scarab, by distracting the Scarab's beam in the Xbox 360 video game Halo Wars.
This works in Single Player and Co-op locally and or on Xbox Live on every difficulty including Easy, Normal, Heroic, and Legendary. Tutorial: 1. Upgrade the Marines to "New Blood" and put a squad of them in either the Sniper Tower in front of the Scarab, or into the one on the right (next to the turret).
When the beam hits the Sniper Tower it will lock on and continuously shoot without hurting or killing the Marines. 2. Send in your vehicles, infantry, and MAC blasts to destroy the scarab without fear of getting hit by the beam.
Tip(s): 1. If you get a vehicle or infantry unit too close to the endpoint of the Scarab's beam it will move off of the Sniper Tower. If this happens, move your unit(s) out of the way and wait for it to lock back onto the Sniper Tower.2.
Sometimes when you get too close to the endpoint of the beam and it becomes dislodged from the Sniper Tower it will only move back and forth a few feet/meters rather than moving around the map. When this happens in front of your base, you can unstick the beam by shooting the Scarab with any of your units or from a MAC blast. Otherwise it'll quickly blast through the protective ruins alongside your base and you'll lose the Mission when your base is destroyed.
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