Cassander proved to be too strong for Polysperchon in Greece. He had obtained large bodies of troops from his Asiatic allies, and he maneuvered and managed these forces with so much bravery and skill, that Polysperchon could not dislodge him from the country. A somewhat curious incident occurred on one occasion during the campaign, which illustrates the modes of warfare practiced in those days. It seems that one of the cities of Peloponnesus, named Megalopolis, was on the side of Cassander, and when Polysperchon sent them a summons to surrender to him and acknowledge his authority, they withdrew all their property and the whole of their population within the walls, and bid him defiance. Polysperchon then advanced and laid siege to the city. After fully investing the city and commencing operations on various sides, to occupy the attention of the garrison, he employed a corps of sappers and miners in secretly undermining a portion of the wall. The mode of procedure, in operations like this, was to dig a subterranean passage leading to the foundations of the wall, and then, as fast as these foundations were removed, to substitute props to support the superincumbent mass until all was ready for the springing of the mine. When the excavations were completed, the props were suddenly pulled away, and the wall would cave in, to the great astonishment of the besieged, who, if the operation had been skillfully performed, knew nothing of the danger until the final consummation of it opened suddenly before their eyes a great breach in their defenses. Polysperchon's mine was so successful, that three towers fell into it, with all the wall connecting them. These towers came down with a terrific crash, the materials of which they had been composed lying, after the fall, half buried in the ground, a mass of ruins.