A game first played in Persia/Iran at dates given from the 6th century BC, or much earlier, to the 1st century AD and originated there. Polo was at first a training game for cavalry units, usually the king's guard or other elite troops. To the warlike tribesmen, who played it with as many as 100 to a side, it was a miniature battle. In time polo became an Iranian national sport played extensively by the nobility. Women as well as men played the game, as indicated by references to the queen and her ladies engaging King Khosrow II Parviz and his courtiers in the 6th century AD.[4] modern day playing cards.