The 150-person team consisted mainly of first-person shooter veterans or longtime "Rainbow Six" players. Despite having prior knowledge on how these types of games work, the team decided to study historic examples of counter-terrorist operations, including 1980's London Iranian Embassy siege, 1977's Lufthansa Flight 181 hijacking, and 2002's Moscow theatre hostage crisis to ensure that the portrayal of these operations was accurate and appropriate. The team also consulted counter-terrorism units, such as the National Gendarmerie Intervention Group (GIGN), for their opinions on how they would react during a hostage rescue situation. According to Xavier Marquis, the game's creative director, having a hostage rescue mission in the game helped create an immersive story. By allowing players to assume control of an operator tasked with saving innocents, it gives them an objective and a priority. They must be careful in dealing with the situation and try their best not to hurt the hostage. This further promotes teamwork between players and prompts them to plan before attacking, and further makes the game more realistic, tense and immersive. To make the game feel more realistic, the team introduced a mechanic called "living hostage" to govern the hostage character's behaviour – e.g., coughing if there is dust in the air or shielding him or herself if there is nearby gunfire.