👉 Thucydides' theory is a philosophical and literary theory that originated in ancient Athens, Greece. It was developed by Thucydides, an Athenian statesman of the 4th century BC, who wrote extensively on military strategy and politics during the Peloponnesian War. In Thucydides' theory, the concept of "the thucydidean sword" refers to a device used in ancient warfare that was intended to be thrown at an opponent's ship or