Sweet Naptime

Sweet Naptime is an achievement in Halo Wars that is unlocked when you put every colony in hibernation at the same time on the 9th mission.

Tips
Put the mission on Easy with all skulls that help the player. Scout out all 4 of the other colonies. Just make a bunch of Gauss Warthogs, put all 4 into hibernation, then kill the main building you should get the achievement right after the cut scene. Trick is to keep the 4 colonies in hibernation then kill the main building the regenerate time is 4 mins. Which is more than enough time to kill them all.

Lock down cobras and elephants next to the colonies, they will shoot the colonies as soon as they respawn.