An army well supplied with camels might carry its provisions and water through the desert, and might intimidate or overpower the few Arab tribes which inhabited it; but, unless the command of the sea was gained and the navigation of the Nile closed, Memphis might successfully resist attack.

Cambyses appears to have perceived with sufficient clearness the conditions on which victory depended, and to have applied himself at once to securing them.

He made a treaty with the Arab Sheikh who had the chief influence over the tribes of the desert; and at the same time he set to work to procure the services of a powerful naval force.

By menaces or negotiations he prevailed upon the Phoenicians to submit themselves to his yoke, and having thus obtained a fleet superior to that of Egypt, he commenced hostilities by robbing her of a dependency which possessed considerable naval strength, in this way still further increasing the disparity between his own fleet and that of his enemy.
Against the combined ships of Phoenicia, Cyprus, Ionia, and AEolis, Egypt was powerless, and her fleets seem to have quietly yielded the command of the sea.

Cambyses was thus able to give his army the support of a naval force, as it marched along the coast, from Carmel probably to Pelusium; and when, having defeated the Egyptians at the last-named place, he proceeded against Memphis, he was able to take possession of the Nile, and to blockade the Egyptian capital both by land and water.
It appears that four years were consumed by the Persian monarch in his preparations for his Egyptian expedition.