Darius, as we have seen, had fled after the disastrous battle of Issus. His terror was so great that he never stopped in his flight until he had reached the other side of the river Tigris, where he still believed himself safe. Instead of going after Darius at once, Alexander first went southward along the coast; for he thought it would be wiser to take all the cities near the sea before he went farther inland, so as to make sure that he had no enemies behind his back.

Marching down through Syria and Phoenicia, Alexander took the cities of Damascus and Sidon, and came at last to Tyre, a prosperous commercial city built on an island at a short distance from the shore. The Tyrians would not open their gates and surrender, so Alexander prepared to besiege the city. As he had no fleet, he began to build a great causeway out to the island.