In middle Greece, Thebes succeeded in uniting Bœotia into a federal state, while its neighbour Athens, which had maintained the unity of the Attic district since the beginning of history, began to annex the neighbouring districts of Megara, Bœotia, and Eubœa, and laid the foundation of a colonial power, as Corinth had formerly done. In the north the Thessalians acquired leadership over all surrounding tribes. In the west, in Sicily, usurpers had founded larger monarchical unified states, especially in Syracuse and Agrigentum. But all these combinations were after all only of very limited extent and by no means firmly united; on the contrary, the weaker communities felt even the loosest kind of federation, to say nothing of dependence, as an oppressive fetter which impaired the ideal of the individual destiny of the autonomous state, and which at least one party,--generally the one that happened to be out of power,--felt justified in bursting at the first opportunity. However, as things lay, the nation found itself forced, with this sort of constitution, to take up the struggle for its political independence. The Greeks of Asia Minor, formerly subjects of the kings of Sardis, had become subjects of the Persian kingdom under Cyrus; the free Hellenes had the most varied relations with the latter, and more than once gave him occasion to intervene in their affairs. The Persian kingdom, which under Darius no longer attempted conquests that were not necessary for the maintenance of its own existence, took no advantage of these provocations until the revolt of the Greeks of Asia Minor, supported by Athens, made war inevitable. After the first attempt had failed Xerxes repeated it on the greatest scale. Against the Hellenic nation, whose alien character was everywhere a hindrance in its path, the Orient arose in the east and the west for a decisive struggle; the Phœnician city of Carthage, the great sea power of the west, was in alliance with the Persian kingdom. Only the minority of the Hellenes joined in the defence; in the west the princes of Syracuse and Agrigentum, in the east Sparta and the Peloponnesian league, Athens, the cities of Eubœa and a few smaller powers. But in both fields of operation the Hellenes won a complete victory; the Carthaginians were defeated on the Himera, in the east Themistocles broke the base of the Persian position by destroying their sea power with the Athenian fleet that he had created, and on the battle-field of Platæa the Persian land forces were defeated by the superiority of the Greek armies of hoplites.