What sequence of events lead Duncan to name MacBeth Thane of Cawdor?

The original Thane of Cawdor was simply known as Thane of Cawdor, that was his title. Thane just meant a lord over a given piece of land. He betrayed King Duncan in the rebellion. Duncan was so impressed with Macbeth's valor in battle that he executed Cawdor and gave his title to Macbeth.