A Pyrrhic victory is a victory with devastating cost to the victor; it carries the implication that another such victory will ultimately cause defeat.
Origin
The phrase is named after King Pyrrhus of Epirus, whose army suffered irreplaceable casualties in defeating the Romans at Heraclea in 280 BC and Asculum in 279 BC during the Pyrrhic War. After the latter battle, Plutarch relates in a report by Dionysius:
The armies separated; and, it is said, Pyrrhus replied to one that gave him joy of his victory that one more such victory would utterly undo him. For he had lost a great part of the forces he brought with him, and almost all his particular friends and principal commanders; there were no others there to make recruits, and he found the confederates in Italy backward. On the other hand, as from a fountain continually flowing out of the city, the Roman camp was quickly and plentifully filled up with fresh men, not at all abating in courage for the loss they sustained, but even from their very anger gaining new force and resolution to go on with the war. – Plutarch
In both of Pyrrhus’s victories, the Romans suffered greater casualties than Pyrrhus did. However, the Romans had a much larger supply of men from which to draw soldiers, so their casualties did less damage to their war effort than Pyrrhus’s casualties did to his.
The report is often quoted as “Another such victory and I come back to Epirus alone,” or “If we are victorious in one more battle with the Romans, we shall be utterly ruined.”
Although it is most closely associated with a military battle, the term is used by analogy in fields such as business, politics, law, literature, and sports to describe any similar struggle which is ruinous for the victor. For example, the theologian Reinhold Niebuhr, writing of the need for coercion in the cause of justice, warned, “Moral reason must learn how to make coercion its ally without running the risk of a Pyrrhic victory in which the ally exploits and negates the triumph.” Further, in Beauharnais v. Illinois, a United States Supreme Court decision involving a charge under an Illinois statute proscribing group libel, Justice Black, in his dissent, warned that “[i]f minority groups hail this holding as their victory, they might consider the possible relevancy of this ancient remark: ‘Another such victory and I am undone.’”