From Halopedia, the Halo wiki
Halo: Combat Evolved Anniversary
In Halo: Combat Evolved Anniversary, the achievement is awarded for completing any level cooperatively on Heroic difficulty. The achievement is represented by two M41 rocket launchers over the difficulty shield in its icon. It is worth 20 gamerscore.
Halo: The Master Chief Collection
In Halo: The Master Chief Collection, the achievement is awarded for completing any level cooperatively on Heroic difficulty in any game. The Xbox achievement icon is the loading image of Awash from Halo 2: Anniversary.
- In both titles, if a player earns the Bro Hammer achievement without this achievement already earned, they will be unlocked together. This is also true for the achievement Standard Operating Brocedure.
- The achievement is a play on the word "Overshield".