Spartan Ops is a mission-based cooperative mode in Halo 4 in which up to four players work as part of a team of SPARTAN-IVs known as Fireteam Crimson performing various objectives. Players' customized loadouts are available during each Spartan Ops chapter and completing a mission gives players XP towards their next rank. Episodes 1-5 are contained in Halo 4's second disc, and episodes 6-10 are available as free downloadable content from the Xbox Live Marketplace.
Spartan Ops requires an Xbox Live Gold Membership to play.
The story takes place in February 2558, 6 months after the events of the Halo 4 Campaign and mainly revolves around SPARTAN-IV Fireteams Majestic and Crimson, who are deployed on the shield world Requiem. There are ten episodes which contain five mission-based chapters each. Each episode is accompanied by a short CGI movie which explains the story.
- Main article: Spartan Ops/Season One/Departure
UNSC Infinity recalls the entirety of her SPARTAN-IV contingent for deployment to the Forerunner world Requiem. Fireteam Majestic is met by Infinity's AI Roland and abruptly becomes aware of their new Commanding Officer, Sarah Palmer. Infinity engages the Covenant Remnant fleet straight out of slipspace deploying frigates and SPARTAN teams into Requiem.
- Main article: Spartan Ops/Season One/Artifact
After the recovery of a Forerunner Artifact by Fireteam Crimson, upon transporting the artifact, it activates creating a scan of Infinity's systems causing a loss in most of the power and gravity. The Infinity began falling into Requiem's opening until Commander Sarah Palmer uses 'physical persuasion' on the artifact granting power to the Infinity and its engines. Dr. Glassman inspects the artifact only to be pulled into it shortly after.
Set sometime after Part 1, SPARTAN-IV Fireteam Crimson are held prisoner by the Covenant Remnant. Spartan Miller and UNSC Infinity's AI Roland manage to track Crimson's location. Spartan Robert Dalton orders a diversionary airstrike allowing Crimson to break free and kill their captors. During their escape they meet with MIA Icebreaker squad led by Lieutenant TJ Murphy who hacks an enemy Phantom allowing Crimson and Icebreaker to escape. Crimson then participate in Ops far beyond enemy lines due to the Covenant Remnant believing the captured Phantom to still be one of theirs. Crimson is then directed to sabotage and gather intelligence similar to what they were usually assigned before their capture.
- Main article: Spartan Ops/Season One/Catherine
- Main article: Spartan Ops/Season One/Didact's Hand
- Main article: Spartan Ops/Season One/Memento Mori
- Main article: Spartan Ops/Season One/Scattered
- Main article: Spartan Ops/Season One/Invasion
- Main article: Spartan Ops/Season One/Expendable
- Main article: Spartan Ops/Season One/Key
- Main article: Spartan Ops/Season One/Exodus
- Completing all the Chapters from Departure on Legendary unlocks the A Legendary Episode achievement.
- Some missions have a Red vs. Blue audio easter egg that can be activated by shooting a hidden radio. Shooting the radio causes the Red vs. Blue opening theme song to play and the Roses vs Violets achievement to unlock.
- A number of the maps in Spartan Ops are reused maps from the Campaign or War Games.
- The additional content from Title Update v1.05 (which includes Champions Bundle content) is not available in Spartan Ops.
- At the beginning of every Spartan Ops cinematic on the bottom right of the screen is a Latin phrase: "Per Mare. Per Terras. Per Constellatum." In English, this translates to, "By Sea. By Land. By Stars."