At this crisis Pericles laid down the rules of policy on which Athens ought to act--rules which required her to decline absolutely to submit to any form of dictation from Sparta. When a principle was at stake, it made no difference whether the occasion was trivial or serious. Athens could face war with confidence. Her available wealth was far greater--a matter of vital importance in a prolonged struggle. Her counsels were not divided by the conflicting interests of allies all claiming to direct military movements and policy. Her fleet gave her command of the sea, and enabled her to strike when and where she chose. If Peloponnesian invaders ravaged Attica, still no permanent injury would be done comparable to that which the Athenians could inflict upon them. The one necessity was to concentrate on the war, and attempt no extension of dominion while it was in progress. War was not yet formally declared when the Thebans attempted to seize Platæa, a town of Boeotia, which had long been closely allied to Athens. The attempt failed, and the Thebans were put to death; but the Platæans appealed to Athens for protection against their powerful neighbour, and when the Athenian garrison was sent to them, this was treated as a _casus belli_. Preparations were urged on both sides; Sparta summoned her allies to muster their contingents on the Isthmus for the invasion of Attica, nearly all the mainland states joining the Peloponnesian league. The islanders and the cities in Asia Minor, on the other hand, were nearly all either actually subject to Athens or in alliance with her. As Pericles advised, the Athenians left the country open to the ravages of the invading forces, and themselves retired within the city. In spite of the resentment of those who saw their property being laid waste, Pericles maintained his ascendency, and persuaded the people to devote their energies to sending out an irresistible fleet, and to establishing a great reserve both of ships and treasure, which were to be an annual charge and brought into active use only in the case of dire emergency. The fleet sailed round the Peloponnese, and the ravages it was able to inflict, with the alarm it created, caused the withdrawal of the forces in Attica. In that winter Pericles delivered a great funeral oration, or panegyric, in memory of the Athenians who had so far fallen gloriously in defence of their country, in which he painted the characteristic virtues of the Athenian people in such a fashion as to rouse to the highest pitch the patriotic pride of his countrymen, and their confidence in themselves, in their future, and in their leader. _II.--Early Successes of Athens_