Why is the bleeding sergeant used and what does he say about the way Macbeth fought?

The bleeding sergeant is used to reveal Macbeth's previous record of brave loyalty to king and country in "Macbeth" by William Shakespeare (Baptized April 26, 1564 - April 23, 1616).

Specifically, Macbeth can be viewed as a good, courageous character whose fatal flaws of ambition and manipulability turn him to evil. The sergeant therefore discusses Macbeth's bravekilling of the traitor Macdonwald and then of Banquo's and Macbeth's winning victory in a bloody battle against Norwegian invaders and Scottish collaborators. In essence, the sergeant indicates that when the going gets tough, Captains Banquo and Macbeth get going. In fact, he mentions Macbeth's efforts as "doubly redoubled" in the face of a resupplied, renewed, ferocious enemy.