[CollegeRepublican]

I think that was Darius III.

[scipioII]

Yes this refers to Darius I. Usurper of Persia after the death of Cyrus. Darius was the one who launched the ill fated attack at Marathon and was the father of Xerxes who was stalled at Thermopolae and defeated at Salamis and Macale by the Greeks.

Alexanders conquered a later descendant....either Darius II or III, nor sure.