Thucydides, History of the Peloponnesian War
Benjamin Jowett, Ed.

76. In the same summer, and immediately after the withdrawal of the Athenians from Megara,¹ the Athenian general Demosthenes arrived at Naupactus with forty ships. [2] A party in the cities of Boeotia, who wanted to overthrow their constitution and set up a democracy like that of Athens, had entered into communications with him and with Hippocrates, and a plan of operations had been concerted, chiefly under the direction of Ptoeodorus, a Theban exile. [3] Some of the democratical party undertook to betray Siphae, which is a seaport on the Crisaean Gulf in the Thespian territory, and certain Orchomenians were to deliver up to the Athenians Chaeronea, which is a dependency of the Boeotian, or as it was formerly called the Minyan, Orchomenus. A body of Orchomenian exiles had a principal hand in this design and were seeking to hire a Peloponnesian force. The town of Chaeronea is at the extremity of Boeotia near the territory of Phanoteus in Phocis, and some Phocians took part in the plot. [4] The Athenians meanwhile were to seize Delium, a temple of Apollo which is in the district of Tanagra and looks towards Euboea. In order to keep the Boeotians occupied with disturbances at home, and prevent them from marching in a body to Delium, the whole movement was to be made on a single day, which was fixed beforehand. [5] If the attempt succeeded and Delium was fortified, even though no revolution should at once break out in the states of Boeotia, they might hold the places which they had taken and plunder the country. The partisans of democracy in the several cities would have a refuge near at hand to which in case of failure they might retreat. Matters could not long remain as they were; and in time, the Athenians acting with the rebels, and the Boeotian forces being divided, they would easily settle Boeotia in their interest. Such was the nature of the proposed attempt.