Ancient Athens developed democracy to a higher level than any other state before modern times. It was the leading cultural innovator of its age. This state is rightly revered for its political and cultural achievements. What is less well known is its extraordinary record of military success. Athens transformed ancient warfare and became one of the ancient world's superpowers. There is a strong case that democracy was a major reason for this success. The military impact of Athenian democracy was twofold. The competition of elite performers before non-elite adjudicators resulted in a pro-war culture, which encouraged Athenians in increasing numbers to join the armed forces and to vote for war. All this was offset by Athenian democracy's rigorous debating of war, which reduced the risks of Athenian cultural militarism. It also made military reforms easier and developed the initiative of the state's generals, hoplites, and sailors. Political scientists have long viewed Athenian democracy as a source of fresh ideas. At present they cannot satisfactorily explain the war-making of modern democracies. Consequently ancient history can provide political science with new lines of enquiry into how democracy affects international relations today.