Then an empire fell into their lap. It began, as most ancient empires did begin, with an alliance gradually transformed into a tyranny. Most Ionian cities had already won their freedom on the defeat of the Persian navy, but some had still to be liberated, and all needed protection for the future. The year after Platæa was spent by the Greek fleets in cruising about the Ægean, doing the work of liberation. At first Spartan admirals were in command, but the Ionians disliked Dorian discipline, and Pausanias, the victor of Platæa, was puffed up with pride and power. So they turned to Athens, whose commanders were Kimon, the rich and generous son of Miltiades, Aristeides the Just, and Xanthippus, the father of Pericles, all men of the aristocracy, but loyal servants of Athens and capable seamen. Thus they formed the Confederacy of Delos, a league of maritime states, Ionians who worshipped the Delian Apollo. On his sacred island was to be the treasury of the league, and there the common synods were to meet. This league Athens soon transformed into an empire. From the first some of its members were too poor to supply the normal unit of subscription, the trireme galley. These, then, contributed money on the assessment of Aristeides. Athens built the ships for them in her own dockyards and sent her collectors round for the money. Soon, with true Ionian slackness, all the states except Chios, Samos, and Lesbos converted their naval contribution into a money payment. States were coerced into joining the league, garrisons and magistrates were sent from Athens to hold them in subjection. Often colonies of Athenian citizens were planted on their territory. When the Persian danger was finally removed by the destruction of the Phœnician fleet at Eurymedon the allies began to contemplate withdrawal. They were very soon taught that membership was not a voluntary privilege. Now the empire of Athens was a naked despotism, only mitigated by the fact that many of the states were permitted to manage their own internal affairs. The treasury of the league was removed from Delos to Athens, and the money was spent at her discretion. Meanwhile the ambitions of Athens had extended with success. She was no longer content with a naval empire. She began to cherish plans of a great colonial dominion in the west; she wanted to eat up her shrunken neighbour, Megara, in order to have an outlet to the Corinthian Gulf; she took Naupactus on those waters as a base, and sent reconnoitring expeditions to Sicily and planned a great Panhellenic colony at Thurii, in South Italy. Moreover, she mixed in the affairs of great foreign Powers like Egypt. She attacked Cyprus and overran Bœotia.