Sri Lanka, March 1 -- History rarely announces itself clearly in the moment. But what has unfolded across the skies of Iran, coordinated US and Israeli strikes characterized by their architects as "pre-emptive" and greeted by much of the world as an act of deliberate aggression, may well be remembered as one of the defining ruptures of the twenty-first century. This was not a war that was forced upon anyone. Analysts have been frank in calling it what it is: a war of choice, prosecuted at a moment perceived as one of Iranian vulnerability, with objectives far more ambitious than anything previously attempted.

The distinction matters enormously. Pre-emption, as a legal and moral concept, demands an imminent and demonstrable threat, not a ...