Exodus 14:5

The people fled - This was a natural inference from the change of direction, which indicated a determination to escape from Egypt. Up to the time when that information reached Pharaoh both he and his people understood that the Israelites would return after keeping a festival in the district adjoining Etham. From Etham the intelligence would be forwarded by the commander of the garrison to Rameses in less than a day, and the cavalry, a highly-disciplined force, would be ready for immediate departure.