After Salamis, Athens rose to a commanding position among the Greek states. Her period of supremacy was brief, lasting less than 75 years, but while it endured it rested on her triremes. In the middle of the fifth century she had 100,000 men in her navy, practically as many as Great Britain in her fleet before 1914. Although the period of Athenian supremacy was short-lived, it is interesting because it produced a great naval genius, Phormio, and because it wrecked itself as Persian sea power had done, in an attempt at foreign conquest. Scarcely had the Persian invasion come to an end when bickering broke out among the various Greek states, much of it directed against Athens. She had small difficulty, however, in maintaining her ascendancy in northern Greece on account of her superiority on the sea, and it was during the half century after Salamis that Athens arose to her splendid climax as the intellectual and artistic center of the world. [Illustration: After Shepherd's _Historical Atlas._ THE ATHENIAN EMPIRE AT ITS HEIGHT--ABOUT 450 B.C.] In 431 began the Peloponnesian War. Its immediate cause was the help given by Athens to Corcyra (Corfu) in a war against Corinth. Corinth called on Sparta for help, and in consequence northern and southern Greece were locked in a mortal struggle. The Athenians had a naval base at Naupaktis on the Gulf of Corinth, and in 429, two years after war broke out, the Athenian Phormio found himself supplied with only twenty triremes with which to maintain control of that important waterway. At the same time Sparta was setting in motion a large land and water expedition with the object of sweeping Athenian influence from all of western Greece and of obtaining control of the Gulf of Corinth. A fleet from Corinth was to join another at Leukas, one of the Ionian Islands, and then proceed to operate on the northern coast of the gulf while an army invaded the province. [Illustration: SCENE OF PHORMIO'S CAMPAIGNS]