How has the relationship between Brutus and Cassius, in Shakespeare's Julius Caesar changed since the beginning of the play?

In Shakespeare's play, Julius Caesar,
Cassius and Brutus have shown different motivations in killing Caesar. They have argued
with one another while each tries to follow his own
vision.

First, the relationship between Brutus and Cassius
is based on a lie. Brutus was concerned that if Caesar became king, it would change him
which would harm Rome. Brutus, with all his faults, put the good of Rome before all
else.

Cassius, on the other hand, approaches
Brutus to join the conspirators in assassinating Caesar. Brutus is
not sure, but Cassius plans to falsify papers that will prove Caesar has committed
crimes against the state of Rome. Ultimately, Brutus joins. Cassius, however, does not
share the noble reasoning that governs Brutus' actions: Cassius
hates Caesar because he once saved Caesar's life and believes he has not been rewarded
enough—that he is treated the same as every other citizen of Rome. His reasons for
killing Caesar are completely selfish.

It is, therefore,
not surprising that the two would fight. At one point, the two fight because Cassius
believes that Brutus has mistakenly judged one of Cassius' men for
"taking bribes." What sits at the center of their fighting, though, is the level of
"love and honesty" the men have for each other—at least from Cassius' perspective. Even
as they make plans to got into battle, they cannot agree upon their
strategy.

Cassius is the one behind the plot to kill
Caesar. He is an excellent judge of men, their strengths, weaknesses, etc. However his
is not completely honest with Brutus, and he also fails to take a stand against Brutus
when he does not agree with him, something he would probably not do with another man.
(Cassius might resent this.) Cassius tricks Brutus into joining the plot, though he
cannot prove any of the criticisms he has of Caesar. The best
Cassius can do is criticize Caesar's physical shortcomings; he cannot admit that
Caesar's leadership and superior military strategies have allowed him to be so
successful as Rome's leader. Cassius agrees with some of Brutus' decisions, though his
heart does not agree. For instance, Cassius wants to kill Mark
Antony and Caesar, but Brutus disagrees, wanting them to be guilty
only of "sacrifice" with Caesar, but not "butchery" which Brutus believes would be the
case if they kill Antony.

Later the two men have a terrible
fight, where Cassius accuses Brutus of no longer loving him; Brutus says he does not
like Cassius' faults. Cassius says that if Brutus no longer loves him, he would prefer
Brutus to kill him there. Cassius says:

readability="26">

There is my
dagger,

And here my naked breast; within, a heart
(110)

Dearer than Pluto's mine, richer than
gold.

If that thou best a Roman, take it
forth;

I, that denied thee gold, will give my
heart.

Strike, as thou didst at Caesar, for I
know,

When thou didst hate him worst, thou lovedst him
better (115)

Than ever thou lovedst
Cassius.

In some ways Cassius
seems rather pitiful in his approach to Brutus; Brutus comments that Cassius too quickly
becomes angry and then becomes calm again. The men brush aside their differences and
they are of one mind again. Brutus then admits that his wife, Portia, has killed
herself.

Perhaps the murder of Caesar begins to take its
toll. Cassius will never truly be able to battle his sense of insecurity, as he felt
with Caesar, and Brutus is an honorable man who killed the leader he loved. Now his wife
is dead. It is no wonder the two have grown apart.