Halo Studios creative director Max Szlagor has revealed that Halo Campaign Evolved will add to the start of Halo Combat Evolved’s story.

He said this in a new interview with GamesRadar:
We are also designing three brand new story missions focused on Master Chief and Sergeant Johnson.
They take place before the events of Combat Evolved, and it’ll be the kind of mission that Chief and Johnson would have gone on during that time period – featuring new environments, enemies, characters, and weapons.
Szlagor also confirmed that these missions happen before Halo Reach too.
While we don’t know how much Halo Studios will change in Halo Campaign Evolved, they’re already signaling that it won’t just be a basic remaster.
They seem determined to reintroduce the franchise properly to a new generation of online gamers. At the same time, these new missions show their intent to expand the world for old and new players alike.
