The maximum number of players in the cooperative mission mode of Warhammer 40,000: Space Marine 2 is three, as stated by the developers from Saber Interactive. In the Warhammer 40,000: Space Marine 2 cooperative mode, known as "Operations," groups of three Space Marines take on multitudes of adversaries in distinctive missions.

With the release of current-generation platforms, Saber Interactive is set to entice new generations of Warhammer 40K enthusiasts, who were first exposed to the power of the Adeptus Astartes over 13 years ago in the original Warhammer 40,000: Space Marine game. Set some time after the events of the original game, Space Marine 2 features Titus of the Ultramarines, one of the most formidable Space Marine chapters to date.

Nevertheless, the Operations mode in Space Marine 2's three-player squad limit is peculiar. The reason behind this, according to Saber Interactive in an interview with PC Gamer, is that Astartes are just too strong to function in a larger group. It was "too easy" to use the new Space Marine 2 cooperative mode with a fourth player added, and Saber was less able to balance the players' complexity levels.

Space Marine 2 Co-op Was "Too Easy," According to Saber Interactive, with four players

Even Space Marines alone are incredibly powerful, which is part of the reason Saber Interactive felt co-op gaming too simple with larger teams. The most formidable soldiers the Imperium can field are Space Marines in the Warhammer 40,000 setting. Creative Manager for Space Marine 2 Yann François claims that Space Marines are "almost invincible." Space Marines, equipped with the greatest weaponry humanity has to offer, augmented by unusual genetic alterations, and dressed in power armour, are practically one-man armies.

Because of this, Saber Interactive found it challenging to balance Space Marine 2's Operations mode by creating a challenge centred around that feeling of invincibility. Sadly, bigger teams in cooperative missions proved to be too much of a "massacre," with four Space Marines easily defeating armies in every scenario. Consequently, Saber Interactive decided that there was a "good number," one that would allow them to convey to gamers the overwhelming allure of the Space Marine faction while also providing a respectable challenge.