One of the lesser known, but more impressive Latin phrases from the Classical era. Adrianos Facchetti, A California litigator who specializes in defamation, explains the meaning:
[In] the Commentaries on the Gallic War, … Caesar described the principle of “murum aries attigit,” which literally means the “The Ram Has Touched the Wall.” It referred to a Roman policy: surrender would be accepted before—but not after the battering ram touched a enemy’s city walls. Wikipedia explains the purpose behind the policy well: “The policy was to act as a deterrent against resistance to those about to be besieged. It was an incentive for anyone who was not absolutely sure that they could withstand the assault to surrender immediately, rather than face the possibility of total destruction.”
While Facchetti uses the term to describe his litigation philosophy, it is nonetheless a powerful and useful metaphor for describing a point of no return in human interactions. Though given its relatively infrequent use, you may find it does not gain quite as much purchase for you as it did for Marc Antony and his legions. But I suppose not everyone can be a Roman General.