It sounds so surgical, so precise, exactly the kind of air attack that only the U.S. Air Force can execute.

A series of B-2 bombers lifts off from Whiteman Air Force Base in Missouri or the island of Diego Garcia in the Indian Ocean. Refueled in the air, they head for a remote mountain in north-central Iran, far from civilians, where they get Iran’s most heavily fortified nuclear site, Fordo, in their sights.

They drop their giant 30,000-pound bunker-busters, one after another, blasting a giant hole down to the centrifuge halls that have been in the bull’s-eye of the American military since President Barack Obama and the leaders of Britain and France revealed the existence of the plant in the fall of 2009, charging Iran with a great “deception.”

Few potential operations, with the possible exception of a Chinese invasion of Taiwan, have been so examined, rehearsed and debated. Technically, the military and geological experts say, it should be doable.

And yet it is full of risks — known unknowns and unknown unknowns, as the former defense secretary Donald Rumsfeld used to say in the context of the Iraq War, another rabbit hole of American military action in the Middle East. That is why it has given pause to every American president who has looked at it for the past 16 years.

President Trump on Wednesday emphasized that he had yet to make a decision to drop what in private he calls “the big one.” But gone was the bellicose tone that characterized his public utterances a day earlier. In its place was a note of caution. “I may do it,” he told reporters on the White House’s South Lawn. “I may not do it. I mean, nobody knows what I’m going to do.”