Firstly, the similarities between the two men at the beginning of the play are that they are both generals in King Duncan's army, fighting the invading forces of the king of Norway and the traitors, Macdonwald and the thane of Cawdor. They are both courageous and respected. They are both admired by not only their men but also by their king. They are both seen as noble and honorable. Both men are, at the start, loyal to their king and country.
It can also be said that both men are naturally suspicious and wary of any possible threats, though for different reasons. Banquo becomes suspicious of Macbeth for he believes that he has taken the witches' predictions too much to heart. He, for example, tells Ross and Angus about Macbeth:
New horrors come upon him,
Like our strange garments, cleave not to their mould
But with the aid of use.
He later also tells Macbeth the following in Act 2, scene 1, when the two speak and Macneth promises that he will ensure Banquo certain benefits if they keep counsel:
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