From Halopedia, the Halo wiki
This article is about the achievement. For the Halo Wars campaign level, see Beachhead (Halo Wars level). For the Halo: Reach Firefight level, see Beachhead (Halo: Reach map).
Beachhead is an achievement in Halo: Combat Evolved Anniversary and Halo: The Master Chief Collection. It is awarded for not losing any Marine allies during the beach landing on The Silent Cartographer, on Heroic difficulty or higher. In the original game it is represented by a white MJOLNIR Mark V helmet over the outline of a plasma grenade; in The Master Chief Collection it is represented by a screenshot of Boarding Action.
The achievement is worth 10 Gamerscore.
The player needs to take the damage for the Marines. Keep moving, and make sure the Marines are behind you. Throw grenades when the Covenant troops are in cover, and the use the pistol when they are far away. Don't let the Marines get close to the Sangheili or the Plasma grenades' blast radius.