Before trusting Delphi with a serious question, Herodotus says, Croesus tested several oracles at once by asking each, on an agreed day, what he was doing at that moment; he had in fact set a tortoise and a lamb to boil together in a bronze cauldron, a thing no reasonable guess could hit. Delphi alone answered correctly, and Croesus responded with lavish gifts, gold ingots and vessels among them, before putting the question that mattered: whether he should march against the Persian empire of Cyrus. The answer came back that if Croesus attacked Persia, he would destroy a great empire. Delphi also advised him to find the strongest of the Greeks and make them his ally, which led him to Sparta.
Reading the oracle as an endorsement, Croesus crossed the river Halys into Persian territory. Cyrus defeated him, took his capital Sardis, and ended the Lydian kingdom. Herodotus reports that Croesus, humbled, sent his own men back to Delphi to reproach the god for the deception. The reply he received, through the oracle's priests, was that the prophecy had been true in exactly the words given: Croesus had destroyed a great empire, his own, and had never asked which empire was meant. The god also pointed to an older debt, the murder of a king by Croesus's ancestor Gyges five generations before, as the deeper cause working itself out, and noted that Apollo had already softened the blow, delaying Sardis's fall by three years and, in some versions of the story, sparing Croesus's life at the pyre.