As Caesar was not to be overcome from the landward side, the exertions of the besiegers were directed to destroy his fleet and cut him off from the sea, by which supplies reached him. The island with the lighthouse and the mole by which this was connected with the mainland divided the harbour into a western and an eastern half, which were in communication with each other through two arch-openings in the mole. Caesar commanded the island and the east harbour, while the mole and the west harbour were in possession of the citizens; and, as the Alexandrian fleet was burnt, his vessels sailed in and out without hindrance. The Alexandrians, after having vainly attempted to introduce fire-ships from the western into the eastern harbour, equipped with the remnant of their arsenal a small squadron, and with this blocked up the way of Caesar's vessels, when these were towing in a fleet of transports with a legion that had arrived from Asia Minor; but the excellent Rhodian mariners of Caesar mastered the enemy. Not long afterwards, however, the citizens captured the lighthouse-island, and from that point totally closed the narrow and rocky mouth of the east harbour for larger ships; so that Caesar's fleet was compelled to take its station in the open roads before the east harbour, and his communication with the sea hung only on a weak thread. Caesar's fleet, attacked in that roadstead repeatedly by the superior naval force of the enemy, could neither shun the unequal strife, since the loss of the lighthouse-island closed the inner harbour against it, nor yet withdraw, for the loss of the roadstead would have debarred Caesar wholly from the sea. Though the brave legionaries, supported by the dexterity of the Rhodian sailors, had always hitherto decided these conflicts in favour of the Romans, the Alexandrians renewed and augmented their naval armaments with unwearied perseverance; the besieged had to fight as often as it pleased the besiegers, and, if the former should be on a signal occasion vanquished, Caesar would be totally hemmed in and probably lost.