The young lion will overcome the older one
On the field of combat in single battle
He will pierce his eyes through a golden cage
Two wounds made one, then he dies a cruel death.
This prophecy was already well known in 1559 when Henry II of France held a three-day knightly tournament in honor of the marriages of his sister Marguerite to the Duke of Savoy and of his daughter to King Philip II of Spain. Henry participated in the events, resplendent in full armor, carrying his great shield decorated with an ornate lion. After winning each round, he would raise the visor of his golden helmet to receive the praises of the crowd.
On the third day, at sunset, Henry prepared for his final bout against Count Montgomery. The bout ended in a draw and, when Henry insisted on a final match, the young count tried to excuse himself, aware of the prophecy. After Henry continued to insist, Montgomery relented.
During the second charge, there was loud crack of broken lances. A splinter from the count's broken lance pierced the king's golden visor and lodged behind his left eye, blinding him and penetrating deep into his brain. He lingered for ten days in agony before dying, fulfilling Nostradamus' most famous prophecy.
Source: Nostradamus: The Complete Prophecies by John Hogue