Among all the general's friends no one possessed the confidence of Othello more entirely than Cassio. Michael Cassio was a young soldier, a Florentine, gay, amorous, and of pleasing address, favourite qualities with women; he was handsome, and eloquent, and exactly such a person as might alarm the jealousy of a man advanced in years (as Othello in some measure was), who had married a young and beautiful wife; but Othello was as free from jealousy as he was noble, and as incapable of suspecting, as of doing, a base action. He had employed this Cassio in his love-affair with Desdemona, and Cassio had been a sort of go-between in his suit: for Othello, fearing that himself had not those soft parts of conversation which please ladies, and finding these qualities in his friend, would often depute Cassio to go (as he phrased it) a courting for him: such innocent simplicity being rather an honour than a blemish to the character of the valiant Moor. So that no wonder, if next to Othello himself (but at far distance, as beseems a virtuous wife) the gentle Desdemona loved and trusted Cassio. Nor had the marriage of this couple made any difference in their behaviour to Michael Cassio. He frequented their house, and his free and rattling talk was no unpleasing variety to Othello, who was himself of a more serious temper: for such tempers are observed often to delight in their contraries, as a relief from the oppressive excess of their own: and Desdemona and Cassio would talk and laugh together, as in the days when he went a courting for his friend.
Othello had lately promoted Cassio to be the lieutenant, a place of trust, and nearest to the general's person. This promotion gave great offence to Iago, an older officer, who thought he had a better claim than Cassio, and would often ridicule Cassio, as a fellow fit only for the company of ladies, and one that knew no more of the art of war, or how to set an army in array for battle, than a girl. Iago hated Cassio, and he hated Othello, as well for favouring Cassio, as for an unjust suspicion, which he had lightly taken up against Othello, that the Moor was too fond of Iago's wife Emilia. From these imaginary provocations, the plotting mind of Iago conceived a horrid scheme of revenge, which should involve both Cassio, the Moor, and Desdemona in one common ruin.