Which Assassin's Creed game introduced the Brotherhood management system and is set mainly in Rome?

Assassin's Creed: Brotherhood introduced the Brotherhood management system and is set mainly in Rome.

Released in 2010, Brotherhood continues Ezio Auditore's story after Assassin's Creed II. Ezio works to weaken the Borgia family and rebuild the Assassin Brotherhood in and around Rome. The city functions as the game's principal open-world environment, with districts that can be liberated from Borgia control.

A central feature lets Ezio recruit citizens, train them, and send them on missions across Europe. Recruits gain experience and ranks, and Ezio can call them during missions. This system expanded the series' idea of an Assassin organization from a background concept into a group the player actively develops.

Brotherhood is often confused with Revelations because both feature Ezio. Revelations is set primarily in Constantinople and focuses on Ezio's later life and Altaïr's legacy. Brotherhood also introduced the competitive multiplayer mode to the main series, adding playable Templar agents and assassination-focused matches.