Banquo is a Scottish general in the king’s army and Macbeth’s friend. With Macbeth, Banquo helps Duncan’s forces claim victory over the king of Norway and the thane of Cawdor. Following the battle, Banquo and Macbeth encounter the witches, who make several prophesies about Macbeth. They 
then speak to Banquo about his own future, saying that Banquo’s descendants will be kings. Unlike Macbeth, who appears to be
fascinated by the weird sisters, Banquo expresses doubts about the witches and their prophesies. He comments to Macbeth, for example, that ”oftentimes, to win us to our harm, / The instruments of darkness tell us truths, / Win us with honest trifles, to betray [us]” (I.iii.123-25).
This unwillingness to subscribe wholeheartedly to the visions of the witches, in addition to Banquo’s demonstrated valor in battle, contribute to the view that Banquo is a virtuous man. Yet Banquo’s virtue is an area of some controversy. A common view is that Shakespeare intended Banquo to be seen as a virtuous character who was not responsible in any way for Macbeth’s murderous actions, despite the fact that the source material from which Shakespeare drew depicts Banquo as a co-conspirator in Duncan’s death. This line of thinking is supported by the popular belief that Macbeth was performed (perhaps even written) for King James I in 1606. Historically, Banquo was an ancestor of King James, and some critics argue that because of this, Shakespeare would not portray him in an unfavorable way. Other observers argue that Banquo’s inaction makes him in part morally responsible for the king’s murder. These critics cite Banquo’s soliloquy following Duncan’s death as evidence of his knowledge of (and therefore at least partial responsibility for) Macbeth’s actions. In this speech Banquo acknowledges to himself his suspicions about Macbeth’s actions: “Thou hast it now: King, Cawdor, Glamis, all, / As the weird women promis’d, and I fear / Thou play’dst most foully for’t” (III.i.1- 3).
Shortly after Macbeth kills Duncan, he remembers the witches’ prophesy regarding Banquo: that Banquo’s descendants would be kings. Macbeth then arranges to have Banquo and his son Fleance murdered. Fleance escapes the attack; Banquo does not.
