Campaign is a mode where the player takes control of one or more characters during the campaign mode of the Splinter Cell series. When played by just one player, the mode is typically called single player or solo. When the mode is played by two people, it is typically called cooperative or coop (for the concept of cooperative feature in the Splinter Cell series, see this).
In Tom Clancy's Splinter Cell, Splinter Cell: Pandora Tomorrow, and Splinter Cell: Chaos Theory, players take control of Splinter Cell agent Sam Fisher, who was part of the Splinter Cell Program started under the top secret branch under the National Security Agency, Third Echelon. In Splinter Cell and Pandora Tomorrow, the player would play in mostly linear levels with objectives they'd have to complete. In Chaos Theory, the levels were not open world, but were slightly more open than the previous games, as well as including secondary objectives that were optional, but would sometimes affect later mission objectives.
In Splinter Cell: Double Agent, players played as Sam Fisher again as an undercover agent deep undercover in an American terrorist cell, John Brown's Army (JBA). There were two main features to the campaign, and two mission types: traditional missions played out liked traditional Splinter Cell missions, similar to Chaos Theory. The other type of mission took place in the JBA Headquarters, where the player had to complete objectives for the NSA while undercover. While the game went on, players had to monitor a "Trust Meter" between both the JBA and the NSA.
In Splinter Cell: Conviction, Sam Fisher returns again but being a rogue Splinter Cell after leaving Third Echelon following the JBA Crisis of 2008. The campaign plays out as past events, as told by Sam Fisher's friend Victor Coste as he's held captive in a Black Arrow interrogation room. With no more reliance on Third Echelon's high-tech gadgets and equipment, Fisher had to use some improvised and new gadgets.
In Splinter Cell: Blacklist, Sam Fisher returns as commander of Fourth Echelon, a brand new initiative that reports directly towards the President of the United States. Players take control of Sam Fisher through most of the game, but Fourth Echelon operative Isaac Briggs appears as the deuteragonist in some sections of the Solo Campaign. There are two sections that Isaac Briggs is taken control by the player: Transit Yards and the final level, Site F.
In Splinter Cell, Splinter Cell: Pandora Tomorrow, Splinter Cell: Chaos Theory, Splinter Cell: Double Agent, Splinter Cell: Conviction, and Splinter Cell: Blacklist, the player takes control of Splinter Cell agent Sam Fisher through the course of the single player aspect of the game. In Splinter Cell: Blacklist, Fourth Echelon operative Isaac Briggs is controlled by the player during part of two separate missions (this also marks the first time a character besides Sam is controlled during the single player mode).
In Tom Clancy's Splinter Cell, the campaign mode was the only mode available in game and did not feature any sort of cooperative modes, or any competitive multiplayer modes. Despite being the only mode available, the first title included both platform exclusive and DLC levels to expand the campaign experience. In Splinter Cell: Pandora Tomorrow, the campaign mode was available along with the first multiplayer mode introduced in the series, Spies vs Mercs. In Splinter Cell: Chaos Theory, the campaign mode featured both a solo campaign as well as a cooperative campaign, marking the first time a cooperative campaign appears in the Splinter Cell series.
In the campaign modes of each Splinter Cell title, difficulty levels are sometimes the same or different depending the respective title. In Splinter Cell and Splinter Cell: Pandora Tomorrow, two difficult modes can be selected by the player: Normal and Hard. In Splinter Cell: Chaos Theory, a harder difficulty setting was introduced as "Expert". Splinter Cell: Double Agent (Version 2) introduced a more difficult setting called "Elite" which further increased the challenge by removing much of the player's ammunition and gadgets. In Splinter Cell: Conviction, 'Hard' was replaced with 'Realistic', and Splinter Cell: Blacklist introduced an even harder difficulty named 'Perfectionist'.
- Two games in particular, Splinter Cell and Splinter Cell: Double Agent, had players complete a training course during single player. In Double Agent, the training was a computer simulation while the training in the first game was not.
- Additionally, the training simulation featured in Double Agent was completely optional and was not important to complete before starting the single player mode.
- Splinter Cell: Pandora Tomorrow is the first and only title to start the game by tasking the player to lock pick out of a pair of handcuffs (which is shown to be part of training/simulation for Sam Fisher).
- Splinter Cell: Chaos Theory and Splinter Cell: Blacklist are the only two games in the series that allow the player to select their loadout and gear before the start of each mission.
- Splinter Cell: Chaos Theory ends the game with the Fisher being submerged in water to save Toshiro Otomo. In the next game, Splinter Cell: Double Agent (Version 1), the player begins the mission by diving into water to infiltrate a Geothermal Plant.
- Splinter Cell: Double Agent (Version 2), Splinter Cell: Essentials, and Splinter Cell: Conviction are the only Splinter Cell games set up as having the entire game having happened in the past. In Splinter Cell: Double Agent (Version 2) the campaign is set up in that Sam Fisher is recalling the events to Lawrence Williams.