7. Have A Look On Americana Encyclopedias:

In its volume 29th, page 596 what is mentioned is Xerxes the great, son of Darius the 1st & Atousa (daughter of Kyrus).... In other part of it, they say Greek always exaggerated about the number of their army & all the time Greek was the beginner of the wars so I think everyone can understand that Iranians never were world conquerors.