The Roman army of occupation also, which had been essentially denationalized by its long abode in Egypt and the many intermarriages between the soldiers and Egyptian women, and which moreover numbered a multitude of the old soldiers of Pompeius and runaway Italian criminals and slaves in its ranks, was indignant at Caesar, by whose orders it had been obliged to suspend its action on the Syrian frontier, and at his handful of haughty legionaries. The tumult even at the landing, when the multitude saw the Roman axes carried into the old palace, and the numerous cases in which his soldiers were assassinated in the city, had taught Caesar the immense danger in which he was placed with his small force in presence of that exasperated multitude. But it was difficult to return on account of the north-west winds prevailing at this season of the year, and the attempt at embarkation might easily become a signal for the outbreak of the insurrection; besides, it was not the nature of Caesar to take his departure without having accomplished his work. He accordingly ordered up at once reinforcements from Asia, and meanwhile, till these arrived, made a show of the utmost self-possession. Never was there greater gaiety in his camp than during this rest at Alexandria; and while the beautiful and clever Cleopatra was not sparing of her charms in general and least of all towards her judge, Caesar also appeared among all his victories to value most those won over beautiful women.

It was a merry prelude to graver scenes. Under the leadership of Achillas and, as was afterwards proved, by the secret orders of the king and his guardian, the Roman army of occupation stationed in Egypt appeared unexpectedly in Alexandria; and as soon as the citizens saw that it had come to attack Caesar, they made common cause with the soldiers.

With a presence of mind, which in some measure justifies his earlier foolhardiness, Caesar hastily collected his scattered men; seized the persons of the king and his ministers; entrenched himself in the royal residence and the adjoining theatre; and gave orders, as there was no time to place in safety the war-fleet stationed in the principal harbour immediately in front of the theatre, that it should be set on fire and that Pharos, the island with the light-tower commanding the harbour, should be occupied by means of boats. Thus at least a restricted position for defence was secured, and the way was kept open to procure supplies and reinforcements. At the same time orders were issued to the commandant of Asia Minor as well as to the nearest subject countries, the Syrians and Nabataeans, the Cretans and the Rhodians, to send troops and ships in all haste to Egypt. The insurrection at the head of which the princess Arsinoe and her confidant the eunuch Ganymedes had placed themselves, meanwhilehad free course in all Egypt and in the greater part of the capital. In the streets of the latter there was daily fighting, but without success either on the part of Caesar in gaining freer scope and breaking through to the fresh water lake of Marea which lay behind the town, where he could have provided himself with water and forage, or on the part of the Alexandrians in acquiring superiority over the besieged and depriving them of all drinking water; for, when the Nile canals in Caesar's part of the town had been spoiled by the introduction of salt water, drinkable water was unexpectedly found in wells dug on the beach.

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 arched 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[42], 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 single occasion vanquished, Caesar would be totally hemmed in and probably lost.

It was absolutely necessary to make an attempt to recover the lighthouse island. The double attack, which was made by boats from the side of the harbour and by the war-vessels from the seaboard, in reality brought not only the island but also the lower part of the mole into Caesar's power; it was only at the second arch-opening of the mole that Caesar ordered the attack to be stopped, and the mole to be there closed towards the city by a transverse wall. But while a violent conflict arose here around the entrenchers, the Roman troops left the lower part of the mole adjoining the island bare of defenders; a division of Egyptians landed there unexpectedly, attacked in the rear the Roman soldiers and sailors crowded together on the mole at the transverse wall, and drove the whole mass in wild confusion into the sea. A part were taken on board by the Roman ships; the most were drowned. Some 400 soldiers and a still greater number of men belonging to the fleet were sacrificed on this day; the general himself, who had shared the fate of his men, had been obliged to seek refuge, in his ship, and when this sank from having been overloaded with men, he had to save himself by swimming to another. But, severe as was the loss suffered, it was amply compensated by the recovery of the lighthouse-island, which along with the mole as far as the first arch-opening remained in the hands of Caesar.

At length the longed-for relief arrived. Mithradates of Pergamus, an able warrior of the school of Mithradates Eupator, whose natural son he claimed to be, brought up by land from Syria a motley army - the Ityraeans of the prince of the Libanus[43], the Bedouins of Jamblichus, son of Sampsiceramus[44], the Jews under the minister Antipater, and the contingents generally of the petty chiefs and communities of Cilicia and Syria. From Pelusium, which Mithradates had the fortune to occupy on the day of his arrival, he took the great road towards Memphis with the view of avoiding the intersected ground of the Delta and crossing the Nile before its division; during which movement his troops received manifold support from the Jewish peasants who were settled in peculiar numbers in this part of Egypt. The Egyptians, with the young king Ptolemaeus now at their head, whom Caesar had released to his people in the vain hope of allaying the insurrection by his means, despatched an army to the Nile, to detain Mithradates on its farther bank. This army fell in with the enemy even beyond Memphis at the so-called Jews'-camp, between Onion and Heliopolis; nevertheless Mithradates, trained in the Roman fashion of manoeuvring and encamping, amidst successful conflicts gained the opposite bank at Memphis. Caesar, on the other hand, as soon as he obtained news of the arrival of the relieving army, conveyed a part of his troops in ships to the end of the lake of Marea to the west of Alexandria, and marched round this lake and down the Nile to meet Mithradates advancing up the river.