(M666) Having thus strengthened his power in Syracuse, he marched against the Sikels, in the interior of the island. But his absence was taken advantage of by the discontented citizens, who attempted to regain their freedom. He returned at once to Syracuse, and intrenched himself in his fortress, where he was besieged by the insurgents. The tyrant was now driven to desperation, and nothing saved him but the impregnable fortifications which he had erected. But his situation was so desperate that his adherents melted away, and he began to abandon all hope of retaining his position. As a last resource, he purchased the aid of a body of Campanian cavalry, in the Carthaginian service, which was stationed at Gela, while he amused the Syracusans, to gain time, by a pretended submission. They agreed to allow him to depart with five triremes, and relaxed the siege, supposing him already subdued. Meanwhile the Carthaginian mercenaries arrived and defeated the Syracusans, already dispersed and divided. Dionysius, finding himself rescued and re-established in his dominions, strengthened the fortifications of Ortygia, and employed his forces, now that Syracuse was subdued, in conquering the Grecian cities of Naxos, Catana, and Leontini. Strengthened at home and in the interior, Dionysius then prepared to attack the Carthaginians, but previously took measures to insure the defensibility of Syracuse. Six thousand persons were employed on a wall three and a half miles in length, from the fort of Trogilus to Euryalus, the summit of the slope of Epipolæ, a high cliff, which commanded the roads to the city. Six thousand teams of oxen were employed in drawing the stones from the quarries. This wall was not like Ortygia, a guard-house against the people of Syracuse, but a defense against external enemies. As it was a great public work of defense, the citizens worked with cheerfulness and vigor, and so enthusiastically did they labor, that the work was completed in twenty days. The city being now impregnable, he commenced preparations for offensive war, and changed his course toward the citizens, pursuing a mild, and conciliatory policy. He made peace with Messene and Rhegium, and married a lady from Locri. He collected all the best engineers, mechanics, and artisans from Sicily and Italy, constructed immense machines, provided arms from every nation around the Mediterranean, so that he collected or fabricated one hundred and forty thousand shields and fourteen thousand breastplates, destined for his body-guard and officers, together with a vast number of helmets, spears, and daggers. All these were accumulated in his impregnable fortress of Ortygia. His naval preparations were equally stupendous. The docks of Syracuse were filled with workmen, and two hundred triremes were added to the one hundred and ten which already were housed in the docks. The trireme was the largest ship of war which for three hundred years had sailed in the Grecian or Mediterranean waters.