In Act III, Iago attempts to convince Othello that Desdemona has been unfaithful to him. Iago plants the seed that Desdemona and Cassio are having an affair. Othello believes Iago but needs to have some type of physical evidence. Iago obtains Desdemona's handkerchief, which was a gift to her from Othello and plans to place it in Cassio's room. This will help convince Othello that his wife has been unfaithful and Othello will probably kill both Cassio and Desdemona.
It seems somewhat hard to believe that in the short time they have been on Cypress that Desdemona and Cassio could have had an affair. Likewise, it is somewhat confusing that Othello quickly assumes that his wife is having an affair. It seems that Iago must be the best manipulator of people that exist in the world. Othello believes everything that Iago tells him concerning Desdemona and Cassio. Never once does Othello doubt anything that Iago tells him. For being a successful general, Othello is very insecure in his marriage.
I wonder how minorities were treated during other periods of time throughout history. It was only seventy years ago that Adolf Hitler tried to eliminate an ethnic group in highly civilized Europe. I question how minorities were treated by the majority in Shakespeare's day, especially in a situation like Othello's mixed race marriage to Desdemona. Finally, is Iago jealous of Othello, or is he simply a racist. If Othello were not a great general, would he ever even had the opportunity to marry Desdemona, considering that he is black, and she is white.