 The Scythians were a group of north Iranian nomadic tribes, speaking an Iranian language (Scythian languages) who had invaded Media, killed Cyrus in battle, revolted against Darius and threatened to disrupt trade between Central Asia and the shores of the Black Sea as they lived between the Danube River, River Don and the Black Sea.Darius crossed the Black Sea at the Bosphorus Straits using a bridge of boats.Darius conquered large portions of Eastern Europe, even crossing the Danube to wage war on the Scythians.