Yet it’s difficult to imagine that the I.A.E.A. can now square Iran’s 2015 declaration with what the Israelis have uncovered. Iran’s mendacity is no longer the informed supposition of proliferation experts such as Mr. Albright. It is — assuming the documents are authentic, as the U.S. has confirmed — a matter of fact that the I.A.E.A. chose to ignore when it gave Iran a free pass under political pressure to move to implement the deal. If the agency cares for its own credibility as a nuclear watchdog, it should decide that Iran’s past declaration was false and that Iran’s retention of the documents obtained by Israel, with all the nuclear know-how they contain, put it in likely breach of the agreement.

As for Iran’s current compliance, of course it’s complying. The deal gave Iran the best of all worlds. It weakened U.N. restrictions on its right to develop, test and field ballistic missiles — a critical component for a nuclear weapons capability that the Iranians haven’t fully mastered. It lifted restrictions on Iran’s oil exports and eased other sanctions, pumping billions of dollars into a previously moribund economy. And it allows Iran to produce all the nuclear fuel it wants come the end of the next decade.

Yes, Iran is permanently enjoined from building a nuclear weapon, even after the limitations on uranium enrichment expire. But why believe this regime will be faithful to the deal at its end when it was faithless to it at its beginning?

Netanyahu’s revelations were plainly timed to influence Donald Trump’s decision, expected later this month, on whether to stay in the Iran deal. Trump is under pressure from the French, British and Germans to stay in it, on the view that, if nothing else, the agreement has kept Iran from racing toward a bomb.

But the deal now in place allows Iran to amble toward a bomb, even as it uses the financial benefits of the agreement to fund (in the face of domestic upheaval and at a steep cost to its own economy) its militancy in Iraq, Lebanon, Yemen and especially in Syria. And Iran’s own nuclear history suggests the country’s leaders have always been cautious in the face of credible American threats, which is one reason they shelved much of their nuclear program in 2003 after the U.S. invaded Iraq.

“When the Iranians fear American power, they either back down or they stall,” says Mark Dubowitz, an expert on Iran sanctions at the Foundation for Defense of Democracies. “When they don’t fear American power, they push forward. With Trump, the question is: Are they going to feel American power, or American mush?”

I opposed the Iran deal, but immediately after it came into effect, I believed that we should honor it scrupulously and enforce it unsparingly. Monday’s news is that Iran didn’t honor its end of the bargain and neither need the United States now. Punitive sanctions combined with a credible threat of military force should follow.