The Cunning of Iago in Othello

So Iago is this extremely interesting, cunning, evil character. But over totally of these traits Iagos jealousy is what drives him to scheme and plot to ready down othello and weave his elaborate web of destruction. Does anyone know exactly when in the play does Iagos intense jealousy come into play? In the very 1st act scene one iago and roderigo are arguing in the streets and iago starts to rant about his hatred for Othello and how Othello passed him up over cassio for advance to ancient.Iago had an enormous amount of battle experience, experience that Othello has witnessed firsthand And I, of whom his eyes had seen the verification At Rhodes, at Cyprus, and on other grounds Christian and heathen, moldiness be beleed and calmed while cassio has no battle experience and scarcely knows the theory of leading men into battle, I have already chose my officer. And what was he? Forsooth, a great arithmetician,One Michael Cassio, a Florentine(A fellow almost damned in a fair wife)Tha t never set a squadron in the field,Nor the plane section of a battle knows More than a spinsterunless the bookish theoric, Wherein the toged consuls sack up propose As masterly as he. Mere prattle without charge is all his soldiership.But he, sir, had th election he has no clue how to put into practise this theory and is therefore unqualified according to iago. Later on in the play iago shows his jealousy of Othello because Othello is rumored to have slept with his wife toIago becomes jealous of cassio getting the procession over him so he devises a plot to get revenge.