Othello is portrayed early in the play as a noble, skilled military leader who is successful at everything he attempts, including marrying the beautiful Desdemona. Yet by the end of the play he is completely overcome with jealousy and rage, to the point of murdering Desdemona and killing himself. Iago drives him to this point by playing on one of Othello's character flaws, his insecurity and jealousy. Whether these feelings were the result of his age or his race, both of which are cited throughout the play, they are clearly present, and they enable Iago to convince him that his wife is unfaithful to him with Cassio. When they encounter Cassio and Desdemona in conversation (with Cassio trying to persuade her to intervene on his behalf with her husband) Iago plants a seed of doubt, intimating that Othello's old lieutenant is attempting to seduce his young wife:
Ha! I like not that.... Cassio, my lord! No, sure I cannot think it That he would steal away so guiltylike Seeing you coming.
Iago is able to manipulate Othello's natural jealousy, and in the process, reduces him to an angry shell of his former self. Whether Othello's nobility earlier in the play is a facade, or whether the Moor simply possessed a tragic flaw that made him susceptible to Iago's scheming is a subject of scholarly debate, but it is clear that Othello, despite his many strengths, is a jealous, insecure man when it comes to his young wife.