They are a set of fast-paced missions in the spirit of "Mile High Club" from Call of Duty 4: Modern Warfare. Originally meant to be the co-op portion of the story campaign, it was spun off into its own separate game mode as Special Ops. This also allowed the designers to add new levels that were interesting, or reuse existing levels with expanded or new objectives, without having to fit them into the singleplayer campaign's storyline, like the campaign missions. The missions can be played solo, split screen or online, with a few being two player exclusive (needing two players in order to play).
The Special Ops mode was created after Infinity Ward attempted to insert co-op into the main singleplayer campaign mode. Infinity Ward said that they wanted to keep the two man feeling from "All Ghillied Up"; to have each others backs and cover each other and work together to complete the objective. They found that attempting to make singleplayer missions co-op compatible was less fun than a regular singleplayer mode and broke the feeling of immersion they were going for. However, instead of scrapping a co-op mode entirely, they created the Special Ops mode with all levels tailored for two players.
Both players cannot die at the same time. For example, if a grenade rolls next to them, one will always survive the blast.
In an oversight for both games, the dialogue said by playable characters when reloading includes "Changing mag!" and "I'm out!", even if their weapon doesn't have a detachable magazine or wasn't empty.