Polytheist is a Biggest of Sin And how to Face them In War

AL-ANFAL (SPOILS OF WAR, BOOTY) : 58-60

8:58. If thou fearest treachery from any group, throw back (their covenant) to them, (so as to be) on equal terms: for Allah loveth not the treacherous.
8:59. Let not the unbelievers think that they can get the better (of the godly): they will never frustrate (them).
8:60. Against them make ready your strength to the utmost of your power, including steeds of war, to strike terror into (the hearts of) the enemies, of Allah and your enemies, and others besides, whom ye may not know, but whom Allah doth know. Whatever ye shall spend in the cause of Allah, shall be repaid unto you, and ye shall not be treated unjustly.