The anonymous letters sent by “Rome” ask for his help ultimately motivates Brutus to join the conspiracy.
Brutus joined the conspiracy against Caesar in order to prevent Rome from the ambitious nature of Caesar in the coming future. While addressing the crowd after the murder of Caesar, Brutus says that he has killed Caesar because of his growing ambition which would be very harmful to the citizens of Rome. He adds that he would never accept that because of one person the whole of the Roman empire would be trapped in the web of slavery.