Mance Rayder was once a man of the Night's Watch before breaking his vows and abandoning his post. He has since become extremely influential amongst the wildlings, who call him the "King-beyond-the-Wall".
Mance was a wildling child taken by the Night's Watch and raised as one of them. He was a loyal member for most of his life until he suffered an injury while ranging and was healed by a wildling woman. While he recuperated, she mended his torn cloak with swatches of red fabric.
Upon returning to the Wall, the Night's Watch commanders required him to replace his mended cloak with another one of uniform black; but this infringement caused him to abandon the Night's Watch and to live with the wildlings in the way he wished.