The officer who spoiled the omen

The night before the battle of Pydna a Roman tribune gathered the legions and told them the Moon was about to be eclipsed, and why, and that it meant nothing.

Gaius Sulpicius Gallus was right on all three counts. When it happened the Romans were calm and the Macedonians across the field were not, reading it as the fall of their king; Livy says so, and the eclipse is why the battle can be dated to the day. Perseus lost his kingdom the next afternoon.