History of the Peloponnesian War

After this, wishing openly now to change the government at Samos to a democracy, Thrasybulus the son of Lycus, and Thrasylus, (for these were the chief leaders in the revolution,) bound all the soldiers, and, most of all, the oligarchical party themselves, by the most solemn oaths, that they would assuredly be governed by a democracy, and live in concord; and also that they would zealously prosecute the war with the Peloponnesians. and would be foes to the Four Hundred, and hold no intercourse with them.

All the Samians too, who were of full age, took the same oath with them; and the soldiers communicated to the Samians all the circumstances, and the probable results of their dangers, thinking that neither for them nor for themselves was there any resource that could save them, but that if either the Four Hundred or the enemy at Miletus should defeat them, they would be destroyed.