Cassius was a senator during the ancient Roman times in history. He died shortly after Julius Caesar’s murder in 44 BC. His full name is Gaius Cassius Longinus. Cassius’s contribution to Caesar’s murder is what we call today – the pot stirrer and manipulator. Cassius comes across during the assassination as just a participant.
However, he began the assassination idea and convinced others to join in. He manipulated them by planting ideas in their heads including relatives of his and of Caesar’s as well. He was even able to convince Brutus who was Caesar’s good friend to join in the assassination. By the time of the assassination, Cassius had moved aside as the leader and the others were angry and took charge.
Cassius convinced Brutus to join the conspiracy in the plot to kill Caesar. Cassius knew that Brutus’s priority was to the people of Rome and Cassius convinced Brutus that Caesar was poison for Rome. He planted a seed in Brutus' mind that Caesar was too powerful and that kind of power causes people to be corrupt.
Caeser also put doubt in Brutus' mind about his intentions. He even convinced Brutus that people were in fear of Caesar's control. Cassius did this by forging several letters from anonymous Roman citizens and placed them around Brutus' home.
These fake letters convinced Brutus that people would be better served if the ‘threat' of the all-powerful Caesar was removed. Cassius saw Caesar's death as a way to gain more power for himself.