Web of Interdependence
Unlike modern “blue-water” naval squadrons, triremes were linked logistically to the coasts. There were no sleeping quarters on board, and the light ships could not carry much food. Thus, the Persian ships were beached every night, so that the oarsmen could eat and sleep in relative comfort. Owing to these logistical factors, the Grand Army [of Xerxes] and the Persian navy were mutually supportive and could not operate independently of each other. The army needed the food carried by the merchant marine, the merchant marine needed the protection of the battle fleet, and the battle fleet needed the secure beachheads established by the army. This web of interdependence was a major weakness of the Persian strategic plan: not only did it limit the tactical maneuverability of the various branches, but it meant that even a temporary collapse in the operational effectiveness of any one of the branches would fatally compromise the goals of the entire expedition.
— Barry S. Strauss and Josiah Ober, The Anatomy of Error, p. 36