Siege of Monteriggioni
The Siege of Monteriggioni was a engagement between the Knights Templar, under the command of Cesare Borgia, and the Order of Assassins, which took place in 1499. Determined to rid themselves of Ezio Auditore da Firenze, the Knights Templar attacked the city of Monteriggioni with an overwhelming force, whilst the city's defenders, led by both Ezio and his uncle – Mario Auditore – held them off[1].
Despite the destruction of many of the Templar's siege machines, the Templars managed to overwhelm the city's defenders and breach the main gates. A mortally wounded Mario Auditore was forced inside the city by Cesare Borgia who, revealing the Apple to be in his possession, proceeded to "invite" Ezio to come to Rome with a shot of his firearm; the shot killed Mario Auditore, whilst Ezio was also shot by a Templar riflemen upon the city walls[1]. When Ezio eventually regained consciousness he made his way to Rome, in pursuit of Cesare Borgia[2].
It would be another five years before he could finally confront Cesare and Rodrigo Borgia in Rome itself[2].