In our home studies today, we learned about Alexander the Great crossing the Hellespont (Dardanelles), and looked it up on wikipedia. We came across this interesting little tidbit about the strait's history:
The ancient city of Troy was located near the western entrance of the strait and the strait's Asiatic shore was the focus of the Trojan War. The Persian army of Xerxes I of Persia and later the Greek army of Alexander the Great crossed the Dardanelles in opposite directions to invade each other's lands, in 480 BC and 334 BC respectively.
Herodotus tells us that c. 482 BC Xerxes I (the son of Darius) had two bridges built across the width of the Hellespont at Abydos in order that his huge army, ostensibly made of 5 million men (most historians put the actual number of this army at closer to 250,000 men, though a second school of thought lends the accounts of Herodotus more credence, bringing the number closer to 400,000), could cross from Persia into Greece. This crossing was named by Aeschylus in his tragedy The Persians as the cause of divine intervention against Xerxes.
According to Herodotus (vv.34), both bridges were destroyed by a storm and Xerxes had those responsible for building the bridges beheaded and the strait itself whipped. The Histories of Herodotus vii.33-37 and vii.54-58 give details of Xerxes' building and crossing of the bridges. Xerxes is then said to have thrown fetters into the strait, given it three hundred lashes and branded it with red-hot irons as the soldiers shouted at the water.