How does Shakespeare rehabilitate Brutus's and Cassius's characters after their deaths in Julius Caesar?

By
act 4 of Shakespeare's historical, Caesar's assassination seems like a
distant memory. Assassins Brutus and Cassius escaped to Greece and raised an army, and within a
year, Rome is embroiled in a civil war. The Triumvirate of Mark AntonyOctavius Caesar (later
known as Augustus, the first Emperor of Rome)and Lepidus rules Rome and its western empire, and
Cassius and Brutus command a rebel army in control of Rome's eastern empire.

In act 4, scene 3, Brutus has cause to remind Cassius about Caesar's assassination
while they argue about bribes paid to Lucius Pella by the Sardians. The argument deteriorates
into personal attacks between Cassius and Brutus. They challenge and threaten each other until
Cassius offers Brutus his dagger and tells him to kill him with it.

Shakespeare is demonstrating that, despite his faults and the role he played in
Caesar's assassination, Cassius is still an honorable man who is willing to die for his beliefs
and for his honor.

Likewise, Shakespeare begins to rehabilitate Brutus by
having him forgive Cassius for challenging him, and he reconciles with Cassius as a friends and
comrade-in-arms.

In act 5, scene 1, Cassius and Brutus agree that if they
should lose the coming battle with Mark Antony's and Octavius's forces they will commit suicide
rather than be taken back to Rome to be debased and dishonored.

The battle
ensues. Cassius mistakenly believes that Mark Antony and Octavius have been victorious, and
Cassius fulfills the vow he made to Brutus. Shakespeare has Cassius killed with his own sword
(demonstrating his honor) by his slave, Pindarus in exchange for his freedom (demonstrating
Cassius's nobility).

Brutus is ultimately defeated by Mark Antony and
fulfills his vow to Cassius by running onto his own sword.

Shakespeare gives
Cassius and Brutus honorable deaths, each of them believing that what they did was right for
Rome, and each of them calling on Caesar as they die:

CASSIUS. Caesar, thou art revenged,
Even with the sword that kill'd thee.
(5.3.45€“47)

BRUTUS. Caesar, now be still;
I kill'd not thee with
half so good a will. (5.5.56€“57)

Nothing more is said
about Cassius, but Shakespeare has Antony speak on Brutus's behalf, extolling his virtues and
validating his motives for assassinating Caesar for the good of Rome:

ANTONY. This was the noblest Roman of them all.
All the
conspirators, save only he,
Did that they did in envy of great Caesar;
He
only, in a general honest thought
And common good to all, made one of
them.
His life was gentle, and the elements
So mix'd in him that Nature might
stand up
And say to all the world, This was a man! (5.5.74€“81)

Shakespeare completes Brutus's rehabilitation by having the
victorious Octavius honor Brutus with a burial befitting a general and a statesman:

OCTAVIUS. According to his virtue let us use him
With all
respect and rites of burial.
Within my tent his bones tonight shall lie,
Most
like a soldier, order'd honorably. (5.5.82€“85)