Battle of Thermopylae

Shortly before the battle, Leonidas turned for a prophecy to the Oracle of Apollo at Delphi.

An excerpt from the article 31 facts about Battle of Thermopylae

An oracle was called a sacred place where the gods, through the intermediary of priests, foretold the future, expressed their will, and advised on private and state matters. The Oracle at Delphi was famous throughout Greece - it was widely regarded as omphalos-the navel of the world. In the temple of Apollo at Delphi, the future was foretold by the Pythias-priestesses raised at the temple from childhood. The Pythia drank water from the sacred spring of Kassotis, then sat on a tripod set over a cleft and, inhaling the fumes emanating from the cleft, gave answers. The prophecy was treated as an oracle from Zeus revealed through Apollo.

When asked by Leonidas, Pythia replied that in the coming war either the king of Sparta would die or the entire country would be overrun by enemies.

The prophecy did not stop Leonidas from facing the Persians.