The Romans, they were to say, had extended their conquests over almost all the rest of the world.

They had sent one army into Egypt before, under the command of Mark Antony, under the pretense of restoring Ptolemy Auletes to the throne.

Now another commander, with another force, had come, offering some other pretexts for interfering in their affairs.

These Roman encroachments, the messengers were to say, would end in the complete subjugation of Egypt to a foreign power, unless the people of the country aroused themselves to meet the danger manfully, and to expel the intruders.
As Caesar had possession of the island of Pharos and of the harbor, Ganymede could not cut him off from receiving such re-enforcements of men and arms as he might make arrangements for obtaining beyond the sea; nor could he curtail his supply of food, as the granaries and magazines within Caesar's quarter of the city contained almost inexhaustible stores of corn.

There was one remaining point essential to the subsistence of an army besieged, and that was an abundant supply of water.