Only moments after Brutus has convinced the people that Caesar had to die for his ambition, Antony makes a speech which has the counter effect. Antony stirs up the people's hearts to a frenzy, a fir of rage over what the conspirators have done.
He mentions the will that Caesar did leave and how he had included something for all the people in it. He shares that Caesar loved the people and proved it by including them in his will.
Antony holds up Caesar's garment and mentions how the conspirator's stabbed Caesar. He mentions that Brutus did burst Caesar's very heart because everyone knows Caesar loved Brutus, the honorable Brutus, Caesar's angel:
For Brutus, as you know, was Caesar's angel.
Judge, O you gods, how dearly Caesar loved him!
This was the most unkindest cut of all;
For when the noble Caesar saw him stab,
Ingratitude, more strong than traitors' arms,(195)
Quite vanquish'd him. Then burst his mighty heart...
Antony's speech is extremely effective. In his words, he causes the people to ban together against the conspirators.
Antony calls the conspirators traitors. In so doing, the people began to side with Antony. Just moments after Brutus speaks, the people are ready to kill him now. A civil war is imminent, and Brutus allowed it to happen by giving Antony permission to speak.