Cassio is a Florentine soldier, serving side by side with Othello and Iago. As a soldier on the field, he is good enough to be Caesar’s right hand. His impressive battlefield skills are exceptionally worthy.
“He is a soldier fit to stand by Caesar and give direction,” Iago said to Montano. He was referring to Cassio’s excellence, highlighting it. He could not help but admire his military achievements, even though he despised the man.
The character of Cassio is surrounded by drama. The audience can see his quick promotion to the lieutenant in the Venetian army. Othello’s initiative to make Cassio lieutenant upsets Iago. To deprive Cassio of his status, Iago develops a vicious plan. It spoils the man’s reputation and denounces Othello about the downfall.
Iago pretends to believe that Cassio is an excellent soldier, worthy to stand by Caesar. However, hints to others that the man isn’t trustworthy. Som Iago complements him to others only to discredit him more naturally and effectively. Besides, Iago counts on Cassio’s alcohol addiction, which may jeopardize Othello’s trust.
In Act II, Scene III, Iago aims to prove Cassio’s incompetency. He gets the lieutenant drunk on purpose and makes Roderigo start a fight. The alcohol brings out Cassio’s hidden nature, and he starts acting inadequately. Taking this opportunity, Iago betrays Cassio:
You see this fellow that is gone before;
He is a soldier fit to stand by Caesar
And give direction: and do but see his vice;
‘Tis to his virtue a just equinox,
The one as long as the other: ’tis pity of him.
I fear the trust Othello puts him in.
On some odd time of his infirmity,
Will shake this island.
(Act II, Scene III)
He states that the lieutenant has to offer many vices, which many do not recognize as virtues. The phrase has a biased meaning that can be misunderstood without the right context. Directly perceived, it is a praise of a high level for every soldier.
In reality, it is a cruel lie aimed to destroy Cassio’s career. And it works, as soon after the drunk Cassio incident, Othello fires him:
I know, Iago,
Thy honesty and love doth mince this matter,
Making it light to Cassio. Cassio, I love thee
But never more be officer of mine.
(Act II, Scene III)
Thus, Iago proves to be a great manipulator. He destroys the career and reputation of the man he hates in one scene. Besides, he is innocent and honest in Othello’s eyes, and only the audience sees the full picture.