Whilst we all rightly presumed that the Master Chief Collection was going to be released with all of the content from previous games at launch, 343 Industries has been very far behind with development, due to server issues and other problems with the new Halo 2 anniversary multiplayer.
As a result, many in-game features and content of the Master Chief Collection has been unavailable since launch, including the Spartan Ops missions that were released as part of Halo 4.
The Spartan Ops missions were a set of in-game objectives that followed a set story and played out like the firefight game type in both Halo: Reach and Halo 3: ODST did. Unlike firefight, Spartan Ops were specially designed to delve into the story that took place whilst the Master Chief was floating about in space, and many players have complained that they are an incredibly important part of Halo 4.
Fortunately enough, 343 Industries have just launched Spartan Ops for the Master Chief Collection in a new patch, and it contains all of the episodes from Halo 4 right at launch - this is a total of 10 co-op based episodes that can now be accessed from the Halo 4 section of the Master Chief Collection.
If you didn't play through the Spartan Ops episodes on the Xbox 360 due to 343's strange release schedule for them, then you should definitely give them a go now that they are on the Xbox One, especially if you are a fan of the Halo universe and it's story.