In Assassin's Creed Brotherhood, Ezio Auditore uses a horse-mounted weapon called the machine gun.
The machine gun appears during a mission in which Ezio attacks a war machine associated with the Borgia forces. It is one of several mechanical devices designed by Leonardo da Vinci and adapted for use in the game's historical-action setting. The weapon is mounted on a horse-drawn platform rather than carried like a modern firearm.
Brotherhood presents Leonardo's inventions as temporary tools that Ezio can use against Cesare Borgia's military power. Other war machines in the game include a tank, a naval cannon, and a flying machine. These sequences are inspired by Leonardo's surviving sketches, but the game substantially fictionalizes their construction, operation, and historical deployment.
The machine gun should not be confused with the hidden gun, a compact Assassin weapon introduced in the series' Renaissance-era storyline. Brotherhood is primarily set in Rome and continues Ezio's conflict with the Borgia family after Assassin's Creed II.