In Assassin's Creed Brotherhood, what organization does Ezio Auditore lead?

In Assassin's Creed Brotherhood, Ezio Auditore leads the Assassin Brotherhood.

The game continues Ezio's story after Assassin's Creed II and places him primarily in Rome. There, he works to rebuild the Brotherhood and weaken the Borgia family, whose political and military power supports the Templar cause. Players can recruit and train new Assassins, then send them on missions across Europe.

The Assassin Brotherhood is the series' central secret society, opposing the Templars' pursuit of order through control. Its members follow a creed built around discretion, freedom, and protecting humanity's ability to choose. The organization is not the same as the Templar Order, the rival faction, even though both groups operate secretly and include historical figures.