At the United Nations on Thursday, the Security Council's capacity to watch over Iran's nuclear program quietly fractured, as Russia and China vetoed a U.S.-backed resolution to extend international inspection mandates. The act was less a single diplomatic event than a symptom of a deeper realignment — one in which the great powers no longer share even a common language for managing nuclear risk. What was once treated as routine oversight has become a theater of geopolitical contest, leaving the world with less visibility into one of its most consequential uncertainties.