(M463) The confederate States at last grew weary of personal military service, and prevailed upon the Athenians to provide ships and men in their place, for which they imposed upon themselves a suitable money-payment. They thus gradually sunk to the condition of tributary allies, unwarlike and averse to privation, while the Athenians, stimulated by new and expanding ambition, became more and more enterprising and powerful. (M464) But with the growth of Athens was also the increase of jealousies. Athens became unpopular, not only because she made the different maritime States her tributaries, but because she embarked in war against them to secure a still greater aggrandizement. Naxos revolted, but was conquered, B.C. 467. The confederate State was stripped of its navy, and its fortifications were razed to the ground. Next year the island of Thasos likewise seceded from the alliance, and was subdued with difficulty, and came near involving Athens in a war with Sparta. The Thasians invoked the aid of Sparta, which was promised though not fulfilled, which imbittered the relations between the two leading Grecian States. (M465) During this period, from the formation of the league at Delos, and the fall of Thasos, about thirteen years, Athens was occupied in maintaining expeditions against Persia, being left free from embarrassments in Attica. The towns of Platæa and Thespiæ were restored and repeopled under Athenian influence. (M466) The jealousy of Sparta, in view of the growing power of Athens, at last gave vent in giving aid to Thebes, against the old policy of the State, to enable that city to maintain supremacy over the lesser Bœotian towns. The Spartans even aided in enlarging her circuit and improving her fortifications, which aid made Thebes a vehement partisan of Sparta. Soon after, a terrible earthquake happened in Sparta, 464 B.C., which calamity was seized upon by the Helots as a fitting occasion for revolt. Defeated, but not subdued, the insurgents retreated to Ithome, the ancient citadel of their Messenian ancestors, and there intrenched themselves. The Spartans spent two years in an unsuccessful siege, and were forced to appeal to their allies for assistance. But even the increased force made no impression on the fortified hill, so ignorant were the Greeks, at this period, of the art of attacking walls. And when the Athenians, under Cimon, still numbered among the allies of Sparta, were not more successful, their impatience degenerated to mistrust and suspicion, and summarily dismissed the Athenian contingent. This ungracious and jealous treatment exasperated the Athenians, whose feelings were worked upon by Pericles who had opposed the policy of sending troops at all to Laconia. Cimon here was antagonistic to Pericles, and wished to cement the more complete union of Greece against Persia, and maintain the union with Sparta. Cimon, moreover, disliked the democratic policy of Pericles. But