...alea iacta est!

In 49 B.C., on the shores of the river Rubicone (Romagna), which marked the border between Italy and Gallia Cisalpine, Julius Cesar stated the famous sentence: “Alea iacta est”, that is: “the dice is cast”. Crossing the Rubicone meant to violate the law that prohibited armed men to enter the Italian soil, hence Cesar’s action marked the beginning of the civil war, which brought the end of the Roman Republic and the beginning of Cesar’s dictatorship.
The sentence still refers to actions that cannot be undone.