Now when the Persians that Aryandes sent from Egypt to avenge Pheretime came to Barce, they laid siege to the city, demanding the surrender of those who were guilty of the murder of Arcesilaus: but the Barcaeans, whose whole people were accessory to the deed, would not yield. The Persians besieged Barce for nine months, digging underground passages leading to the walls, and making violent assaults. As for the tunnels, a blacksmith discovered them by the means of a bronze shield, and this is how he found them: carrying the shield around the inner side of the walls, he struck it against the ground of the city; all the other places which he struck returned a dull sound; but where there were tunnels, the bronze of the shield rang clear. Here the Barcaeans made a counter-tunnel and killed those Persians who were digging underground. Thus the tunnels were discovered, and the assaults were repelled by the townsfolk.