President Donald Trump explained his demand for a ceasefire between Israel and Iran with one of the most pungent presidential comments ever made about the Middle East: “We basically have two countries that have been fighting so long and so hard that they don’t know what the f--- they’re doing,” he told reporters on Tuesday morning.

Assuming that Trump can make the two sides stop shooting, what’s next is a period of negotiations. In this phase, Israel knows what it wants - a verifiable, ironclad agreement to prevent Iran from ever producing a nuclear weapon. If Iran won’t agree to dismantle what’s left of its nuclear infrastructure and remove its existing stockpile of highly enriched uranium, this war could start again.

Negotiators will confront this essential problem: Iran has been lying about its activities for more than 20 years. It said it wasn’t trying to make a bomb even as it allegedly gathered - and regathered - its top scientists to push toward weaponization. It claimed to be leveling with the International Atomic Energy Agency, but the IAEA concluded last month that it wasn’t.

Israeli intelligence, backed by IAEA investigations, shows that after Iran ceased a weaponization program known as Amad in 2003, it secretly reconstituted a new effort to pursue similar research. The Iranians moved equipment from one set of secret sites to other covert locations, covering their tracks to evade IAEA inspectors, Israel and IAEA found. When Israel assassinated nuclear-weapons scientists, Iran recruited new ones.

This renewed push to make a bomb was probably the trigger for the devastating war that Israel began on June 13 and ended, at least temporarily, with Monday night’s ceasefire.

Israeli intelligence on Iranian weaponization was shared with me by a source familiar with the reports. Much of it tracks IAEA reports published on June 12 with the agency’s stern warning that it couldn’t “provide assurance that Iran’s nuclear programme is exclusively peaceful.” Trump has received much more detailed information from Israel, and officials say that’s why he stated last week that Iran was actively seeking to build a weapon, despite a statement to the contrary in March by his own director of national intelligence, Tulsi Gabbard. Intelligence reporting on Iran’s weaponization program has a cat-and-mouse element, but sources familiar with Israeli intelligence shared with me a timeline showing what they believe happened .

The Amad bombmaking effort started around 2000, Israeli analysts believe. At secret sites in Varamin and Lavisan-Shian around Tehran, the Iranians explored highly technical problems.

The CIA revealed this weaponization effort in 2007 but concluded that it had stopped in 2003. But the IAEA later found evidence that equipment from the secret Amad sites had been shifted after 2003 to a warehouse in Turquzabad, near Tehran. When Israel discovered the cache of Amad documents in 2018, the nuclear gear was moved once again, Israeli and IAEA documents indicate.

Iran’s renewed weaponization program was called SPND, known in English as the Organization of Defensive Innovation and Research, according to the Israeli document. SPND’s key sites were at Shariati, in Tehran, and Sanjarian, near Parchin in southeastern Iran. The Shariati complex “is part of Iran’s concealment and deception efforts.” The site was struck by Israeli jets on June 13, along with its chief Mansour Asgari, an Iranian physicist.

Iran’s alleged weaponization infrastructure is now in ruins. Israel has destroyed the equipment - and killed the researchers - that were part of what appears to have been a secret bombmaking effort dating back 25 years. The IAEA’s public conclusion this month that “Iran did not declare nuclear material and nuclear-related activities at … Lavisan-Shian, Varamin, and Turquzabad” is nearly as damning as Israel’s secret intelligence dossier. Any future nuclear agreement with Iran must reliably ban any restart of these activities.

The most urgent postwar challenge will be finding - and destroying - Iran’s stockpile of 400 kilograms of 60 percent enriched uranium, which could become fuel for a “dirty bomb” in weeks if it isn’t controlled. Iran’s Isfahan nuclear facility, where this material was thought to be held, was bombed by both Israel and the United States. But the New York Times reported that IAEA director Rafael Grossi believed it had been moved before the attack.

Israeli and American sources say they know where the 400 kilograms are located. We can only hope so. They need to find it - quick.

David Ignatius is a Washington Post columnist.