The Athenian coup of 411 BC was a revolutionary movement during the Peloponnesian War between Athens and Sparta that overthrew the democratic government of ancient Athens and replaced it with a short-lived oligarchy known as The Four Hundred. The oligarchs plotted two coups: one at Athens and one at Samos, where the Athenian navy was based. The coup at Athens went forward as planned, and "[o]n the fourteenth day of the Attic month of Thargelion, June 9th, 411, ... the [conspirators] seized the reality of power." The city came under the control of The Four Hundred oligarchic government.