Wait, what? Yes. When you pick up your copy of Reach on September 14, you’ll be able to enlist the help of a random soldier and fight across the game’s entire campaign.
For reference, Halo 3 didn’t include campaign matchmaking (much to my annoyance). You could hop into a game with an Xbox Live friend, but you couldn’t search for a buddy. Also, Halo games on Legendary difficulty are notoriously difficult and the decision to include matchmaking for campaign will make sure no one has to play alone.