The History of Darius the Great

Darius led the first Persian army into Europe by means of pontoon bridges, or boats hitched together for passageway over water. It's quite a feat of engineering for their time and it allowed the bulk of the Persian army to travel over land, while the navy transported others and supplies via the sea. Once on the other side at Byzantium, Darius erected two stelae made of white stone, one engraved with a searing and writing, and the other with Greek. They may not have been found, but obviously it was erected as propaganda. This records that on the stelae it read his army in Calvary numbered 700,000, with 600 ships.