(below, the great American actor Paul Robeson and Peggy Ashcroft in a scene from the London, 1930 production of Othello in London.)
"Othello" was likely written by Shakespeare sometime around 1604, at least that is when it was recorded as being first performed. It is taken from a short story by an Italian writer named Giraldi Cinthio, but seems considerably improved by the playwright based on the available English version, which is rather a rambling and disjointed tale. A friend of mine who has studied Italian literature called the story a "hack job".
Shakespeare's "Othello" is direct and precise by contrast---we see a story set in Venice and later in Cyprus of a great general who is a Moor and a converted Christian who does great service to the Venetian Republic. Despite his great travails of a life in exotic places and in countless battles, he is taken in by Iago, a villain of rare power who seemingly is willing to destroy all those around Othello and then himself and will do anything and use anyone--even his own wife, Emilia--to set the course of this evil plot involving a misplaced handkerchief, invidious gossip, false and misleading interpretations of simple chivalrous gestures, and literal back-stabbing of his fellow officers.
Iago knows the weaknesses of all those around him, and yet no one suspects him until they are wounded or wronged beyond measure.
What drives Iago? Is it just because he is an ensign and is past up for promotion to lieutenant by a younger man, Cassio? It hardly seems enough of a reason to justify the deviousness and malice in the way Iago takes advantage of Othello's trust and twists him into a terrible crime.
A lot of theories are out there about this--racism, sexual attraction to either Desdemona or maybe Othello himself, but Shakespeare doesn't seem to me to be too worried about any specific reason. Othello is a great man with a gaping blind spot for the virtue of his new wife, and so his fall will be pitied because it is from such a height that the falls, and that, unlike, say, Hamlet who doubts everybody, the Moor's inherent trust in Iago is so abused.
I wondered when I last read this play if Iago is,simply, evil for the sake of being evil. This makes the play perhaps the most modern of the great tragedies of Shakespeare--we live in a world where sociopaths and serial killers haunt our media. Like the scorpion in Franz Kafka's fable from "The Trial" about the reptile killing a frog while on his back in the middle of a stream, even though the scorpion himself will die. It is just Iago's nature and no explanation therefore could be seen as having a purpose. How else, perhaps, to explain the speech here by Kenneth Branagh in a 1995 version of the play:
Here is from the Third Scene of the First Act, where Othello speaks to the Venetian Senate and his new father-in-law, Brabentio, a worthy of the city, on how he and the older man's daughter were secretly wed. This is from Orson Welles' 1952 version, and it also my favorite speech in the play.