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142 encouraged the Athenians to strengthen their naval armament and to perfect themselves in naval discipline, for with Themistocles he was convinced that the supremacy of Athens must depend chiefly upon her fleet.

As a part of his maritime policy, Pericles persuaded the Athenians to build what were known as the Long Walls,—great ramparts between four and five miles in length,—which united Athens to the ports of Piræus and Phalerum. Later, as a double security, a third wall was built parallel to the one running to the former harbor. By means of these walls Athens and her ports, with the intervening land, were converted into a vast fortified district, capable in time of war of holding the entire population of Attica. With her communication with the sea thus secured, and with a powerful navy at her command, Athens could bid defiance to her foes on sea and land.

Events leading up to the Thirty Years' Truce.—At the same