early as the 470s BC the inhabitants started building outside the walls. The complete population of its territory approximately numbered 250,000 in 415 BC and the population size of the city itself was probably similar to Athens. Gelo was succeeded by his brother Hiero, who fought against the Etruscans at Cumae in 474 BC. His rule was eulogized by poets like Simonides of Ceos, Bacchylides and Pindar, who visited his court. A democratic regime was introduced by Thrasybulos (467 BC). The city continued to expand in Sicily, fighting against the rebellious Siculi, and on the Tyrrhenian Sea, making expeditions up to Corsica and Elba. In the late 5th century BC, Syracuse found itself at war with Athens, which sought more resources to fight the Peloponnesian War. The Syracusans enlisted the aid of a general from Sparta, Athens' foe in the war, to defeat the Athenians, destroy their ships, and leave them to starve on the island (see Sicilian Expedition). In 401 BC, Syracuse contributed a force of 300 hoplites and a general to Cyrus the Younger's Army of the Ten Thousand. Then in the early 4th century BC, the tyrant Dionysius the Elder was again at war against Carthage and, although losing Gela and Camarina, kept that power from capturing the whole of Sicily. After the end of the conflict Dionysius built a massive fortress on Ortygia and 22 km-long walls around all of Syracuse. Another period of expansion saw the destruction of Naxos, Catania and Lentini; then Syracuse entered again in war against Carthage (397 BC). After various changes of fortune, the Carthaginians managed to besiege Syracuse itself, but were eventually pushed back by a pestilence. A treaty in 392 BC allowed Syracuse to enlarge further its possessions, founding the cities of Adranon, Tyndarion and Tauromenos, and conquering Rhegion on the continent. In the Adriatic, to facilitate trade, Dionysius the Elder founded Ancona, Adria and Issa. Apart from his battle deeds, Dionysius was famous as a patron of art, and Plato himself visited Syracuse several times, where Dionysius, offended by Plato's daring to disagree with the king, imprisoned the philosopher and sold him into slavery. His successor was Dionysius the Younger, who was however expelled by Dion in 356 BC. But the latter's despotic rule led in turn to his expulsion, and Dionysius reclaimed his throne in 347 BC. Dionysius was besieged in Syracuse by the Syracusan general Hicetas