"This play was most likely written in 1606, early in the reign of James I, who had been James VI of Scotland before he succeeded to the English throne in 1603. James was a patron of Shakespeare’s acting company, and of all the plays Shakespeare wrote under James’s reign, Macbeth most clearly reflects the playwright’s close relationship with the sovereign. In focusing on Macbeth, a figure from Scottish history, Shakespeare paid homage to his king’s Scottish lineage. Additionally, the witches’ prophecy that Banquo will found a line of kings is a clear nod to James’s family’s claim to have descended from the historical Banquo." -- "Macbeth," SparkNotes.com