In Act IV, Scene I, Brutus and Cassius are the generals of two armies set out to defeat the armies of Antony and Octavius for control of Rome. They are allies, but they argue over the pettiest of issues. First, Cassius is upset with Brutus because he punished Lucius Pella for taking bribes despite Cassius' wishes to have him pardoned. Brutus in return accuses Cassius of becoming greedy and corrupt just like Lucius Pella. They then engage in a bout of name calling where they argue about which of the two is the better soldier. Next, Brutus accuses Cassius of denying him a request to borrow money. Cassius denies this and credits it up to miscommunication due to an incompetent messenger. Cassius accuses Brutus of not believing his good will based on their past friendship and Brutus argues that Cassius is too hot-headed. They go on in this fashion until calmer heads finally prevail and they realize they must work together against the common enemy.
In Act Four, Scene 3, Brutus and Cassius argue over several matters before they forgive each other and make up. Cassius is initially upset at Brutus for condemning a man named Lucius Pella for taking bribes from the Sardinians. Cassius had even written a letter on Pella's behalf asking Brutus to ignore the offense, but Brutus proceeded to condemn Pella. Brutus then accuses Cassius of being greedy and accepting bribes in exchange for positions. Brutus then mentions that Cassius's dishonorable actions undermine the real reason why they assassinated Caesar. Cassius feels offended by Brutus's accusations and threatens to harm him. Brutus dismisses Cassius's threats and brings up the fact that Cassius did not give him money to pay his soldiers. Brutus believes that Cassius has been hoarding money, which is why Cassius never paid him. However, Cassius claims that he never denied Brutus and says that the messenger incorrectly communicated his response. Cassius feels overwhelmed by Brutus's accusations and even offers Brutus an opportunity to kill him. Fortunately, cooler heads prevail, and the two partners make up.