Peloponnesian War

The Peloponnesian War (431–404 BCE) pitted Athens and its naval empire against Sparta and its land-based alliance. Thucydides documented the whole thing in real time — his history is still considered one of the greatest works of nonfiction ever written. A devastating plague hit Athens early on, killing Pericles. Sparta eventually won, but the war weakened all of Greece so badly it set the stage for Macedon to take over. Classic 'everybody loses' scenario.