Final answer:
Iago manipulates events and perceptions to cause Cassio's dismissal as lieutenant by Othello, as part of his larger plan for revenge in Shakespeare's play.
Step-by-step explanation:
The character Iago from Shakespeare's play Othello performs a series of deceitful actions which lead to Cassio's dismissal as Othello's lieutenant.
Iago orchestrates a fight involving Cassio, which results in Cassio's brawling. Iago then misrepresents the situation to Othello, exaggerating Cassio's misconduct, which leads Othello to believe that Cassio is unfit for his role.
This manipulation is part of Iago's larger plan to seek revenge against Othello for passing him over for promotion in favor of Cassio. Thus, Iago's malicious scheming causes Cassio to lose his position.