Meantime, the Persians were advancing. Lacrates the Theban set himself to reduce Pelusium, and, having drained dry one of the ditches, brought his military engines up to the walls of the place. In vain, however, did he batter down a portion of the wall--the garrison had erected another wall behind it; in vain did he advance his towers--they had movable towers ready prepared to resist him. No progress had been made by the besiegers, when on a sudden the resistance of the besieged slackened. Intelligence had reached them of Nekht-nebf's hasty retreat. If the king gave up hope, why should they pour out their blood to no purpose? Accordingly they made overtures to Lacrates for a surrender upon terms, and it was agreed that they should be allowed to evacuate the place and return to Greece, with all the goods and chattels that they could carry with them. Bagoas demurred to the terms; but Ochus confirmed them, and Pelusium passed into the possession of the Persians without further fighting. About the same time Mentor had proceeded southwards and laid siege to Bubastis. Having invested the town, he caused intelligence to reach the besieged that Ochus had determined to spare all who should surrender their cities to him without resistance, and to treat with the utmost severity all who should fight strenuously in their defence. By these means he introduced dissension within the walls of the towns, since the native Egyptians and their Greek allies naturally distrusted and suspected each other. At Bubastis the Egyptians were the first to move. The siege had only just begun when they sent an envoy to Mentor's colleague, Bagoas, to offer to surrender the town to him. But this proceeding did not suit the Greeks, who caught the messenger, extracted from him his message, and then attacked the Egyptian portion of the garrison and slew great numbers of them. The Egyptians, however, though beaten, persisted, established communication with Bagoas, and fixed a day on which they would receive his forces into the town. Mentor, who wished to secure to himself the credit of the surrender, hereupon exhorted his Greek friends to be on the watch, and, when the time came, to resist the movement. This they did with such success that they not only frustrated the attempt, but captured Bagoas himself, who had ventured within the walls. Bagoas had to implore the interference of his colleague on his behalf, and was obliged to promise that henceforth he would attempt nothing without Mentor's knowledge and consent. Mentor gained his ends, had the credit of being the person to whom the town surrendered itself, and at the same time established his ascendancy over Bagoas. It is clear that had the Egyptians possessed an active and able commander, advantage might have been taken of the jealousies which divided the Persian generals from their Greek colleagues, to bring the expedition into difficulties.