An eclipse loses Athens a war

The Athenian army at Syracuse was finally packed and ready to sail home when the full moon went dark, and the soothsayers said wait thrice nine days.

Nicias waited. The Syracusans used the time to block the harbour mouth, and the fleet that had come to conquer Sicily was destroyed trying to get out; Thucydides calls it the greatest reverse in Greek history. Two thousand years later the same sky can be recomputed, and it says the same thing: full, and eclipsed.