Battle of Thermopylae aware that his force was being outflanked, dismissed the bulk of the Greek army and remained to guard their retreat with 300 Spartans and 700 Thespians, fighting to the death. Others also reportedly remained, including up to 900 helots and 400 Thebans; these Thebans mostly reportedly surrendered. Themistocles was in command of the Greek Navy at Artemisium when he received news that the Persians had taken the pass at Thermopylae. Since the Greek strategy required both Thermopylae and Artemisium to be held, given their losses, it was decided to withdraw to Salamis. The Persians overran Boeotia and then captured the
Thermopylae shoreline has also advanced over the centuries because of the sedimentary deposition. The level of the Malian Gulf was also significantly higher during prehistoric times and the Spercheios River was significantly shorter. Its shoreline advanced by up to 2 kilometers between 2500 BC and 480 BC but still has left several extremely narrow passages between the sea and the mountains. The narrowest point on the plain, where the Battle of Thermopylae was probably fought, would have been less than wide. Between 480 BC and the 21st century, the shoreline advanced by as much as in places, eliminating the narrowest points