Commissars are special Imperial officers assigned to Imperial Guard regiments and Imperial Navy ships, whose purpose is to enforce discipline and devotion to the Emperor of Mankind.
They are tasked with the duty to maintain the morale of the troops during their massive campaigns, often in the face of staggering casualties. The Commissar is empowered to use any means necessary to ensure the loyalty and moral purity of his or her charges, including overriding or even executing a regiment's commanding officer if necessary, and so is regarded with a mixture of fear and admiration by rank-and-file Guardsmen -- and more than a few of their officers.
Music Used - Imperial Guard Theme from Dawn of War - Winter Assault
Link - www.youtube.com/watch?v=mhqWHIq-aZw
More on Imperial Commissars here: - warhammer40k.wikia.com/wiki/Commissar