When conspiring with Cassius to kill Caesar, Brutus tells Cassius that it was best not to kill Mark Antony because he wanted the Roman people to view the assassination of Caesar as an honorable gesture. If they assassinated Mark Antony as well, the public would view them as cruel, blood thirsty and vindictive murderers. Brutus also believed that Caesar's death would diminish Mark Antony's power.
In William Shakespeare's play "Julius Caesar," the conversation between the conspirators occurs in Act II, Scene I. Cassius is afraid of Mark Antony, and he wants to kill him along with Caesar. However, Brutus convinces him that this is unnecessary.
The historical basis for this play was the conspiracy to assassinate Caesar that involved many Roman senators. Brutus and the conspirators killed Caesar on the Ides of March in 44 B.C.