Octavius, Antony, and their army are waiting on the battlefield.
Antony thinks that Brutus and Cassius are attacking them in order to make themselves look braver than they are. A messenger alerts them that the opposing army is approaching.
Antony gives Octavius an order about how to advance his troops, which Octavius disputes. When Antony asks why Octavius is arguing with him, he replies, "I do not cross you, but I will do so.”
Brutus’s and Cassius’s army meets Antony’s and Octavius’s army on the battlefield, and they exchange taunts. Brutus and Cassius mock Antony as an untested soldier, a bee who is all “buzz” and no sting. Antony and Octavius call Brutus and Cassius hypocrites and traitors. Antony and Octavius exit in disgust.
As Brutus steps aside with Lucilius, Cassius talks with Messala.
Cassius says that, although he’s an Epicurean and previously gave little credit to omens, he has changed his mind—carrion birds have been flying above the army and looking down at them as if they’re prey.
When Brutus returns, Cassius says that, although he’s hopeful about the battle, in the event that they lose, this will be the last time he and Brutus speak together.
Brutus says that if they lose, his Stoic outlook will prevent him from committing suicide. However, neither will he be content to be led as a defeated captive through the streets of Rome. The two say farewell to each another.