Before dawn in the US on Saturday, plane spotters using flight tracker apps noticed B-2 stealth bombers based in Missouri flying to the Pacific, sparking speculation they were heading to Guam to prepare for an attack on Iran.

As experts debated why the B-2s were flying towards Guam and not Diego Garcia, an Indian Ocean location closer to Iran where the US and UK have a base, the US was already conducting a top-secret attack on Iran.

Very early Saturday morning eastern time, seven other B-2s took off from Whiteman Air Force Base in Missouri. Unlike the planes that flew to the Pacific and made themselves detectable at times, the seven B-2s flew east in stealth mode. Roughly 18 hours later, they dropped 14 massive bunker-buster bombs on two of Iran’s three nuclear sites that were hit in the strikes.

After the strikes on Fordow, Natanz and Isfahan, US defence secretary Pete Hegseth said Operation Midnight Hammer involved very tight operational security and “misdirection”.

“The scope and scale of what occurred . . . would take the breath away of almost any American if you had an opportunity to watch it in real time,” Hegseth said. “Tehran is certainly calculating the reality that planes flew from the middle of America . . . completely undetected over three of their most highly sensitive sites and we were able to destroy nuclear capabilities.

Hegseth was flanked by General Dan “Razin” Caine, chairman of the joint chiefs of staff, who said the B-2 bombers that flew west to the Pacific were a “decoy” designed to ensure “tactical surprise”.

Caine said the “deception effort [was] known only to an extremely small number of planners and key leaders” in Washington and at US Central Command, which overseas US forces in the Middle East.

Mark Kimmitt, former deputy director for strategy and plans at Centcom, said the operational security was impressive. “In my years in the military and government, I never saw it this tight.”

Doug Birkey, head of the Mitchell Institute for Aerospace Studies, said the bombers used a “conceal-reveal” tactic with some planes making themselves detectable at times, while the others stayed stealth.

Caine said the strikes started at 12.30am Sunday in Iran when a US submarine launched more than 24 Tomahawk cruise missiles at Isfahan as the B-2s entered Iranian airspace. The B-2s hit their targets between 2.10am to 2.35am. Shortly afterwards, the tomahawks reached Isfahan — timed to ensure that the B-2s maintained an element of surprise.

Caine said the bombers and their accompanying refuelling aircraft and fighter jets — known as the “strike package” — had flown in and out of Iranian airspace without coming under any fire.

“This was a carefully crafted mission which utilised significant operational deception, notably, sending a decoy set of B-2 bombers to Guam,” said James Stavridis, a former US Supreme Allied Commander in Europe. “The media fixated on the Guam movement, and I suspect it made the Iranians think they had another few days.”

Joseph Votel, who commanded Centcom for the first two years of Donald Trump’s first presidency, said flying B-2s from Missouri enhanced secrecy. “By deploying directly from the US, the joint force was doing everything it could to minimise detection, which is very smart,” he said.  

Kimmitt said sending B-2s to Guam was a “nice little head fake”, but that the key strategic deception came earlier. “The ultimate deception was Trump laying down a two-week timeline for negotiations and then attacking Iran three days later, a classic Trojan horse,” he said.

On Thursday, Trump gave Tehran a “maximum” of two weeks to reach a nuclear deal with the US, suggesting that a strike was not imminent. Two days later, the US struck the three Iranian nuclear facilities.

But there were signs that Trump had made his decision, even if he had not made the final order, by Thursday. Three people familiar with the situation said he left leaders at the G7 in Canada last weekend with the impression that he would strike Iran.

They said he had presented options to other leaders. A fourth person said he told the group that de-escalation had not and would not work. He told the leaders that any attack would involve one run against Iran.

“It was clear to me that he was already preparing his talking points,” said one of the people.

However, following the G7, UK Prime Minister Sir Keir Starmer said Trump said “nothing . . . to suggest he’s about to get involved in this conflict”.

When the UK, France, Germany and the EU held talks with Iran on Friday, UK foreign secretary David Lammy was unaware of the imminent attack. But he tried to convince Iran that it could not afford to slow-walk negotiations with Washington, according to one person close to the talks. “Lammy really tried to get the Iranian delegation to focus on the word ‘within’ after Trump said, ‘within two weeks’,” the person said.

Several people said Trump seemed to have been convinced that the risks had been significantly reduced since Israel had degraded Iran’s air defences with its attacks in the days prior to the US mission.

“The administration’s elaborate deception abetted surprise and therefore reduced risk to the operation but given that Israel had already established air dominance and decimated Iran’s military leadership perhaps not by much,” said Kori Schake, head of foreign and defence policy at the American Enterprise Institute.

At the press briefing, Caine said the US “took advantage of some of the preparatory work that’s been done [by Israel] over the past week and a half in terms of access [and] approach”.

Birkey said the F-35 fighter jets that Israel had used in its campaign had played a huge role. “The F-35s are incredible information sponges that suck up so much intelligence” on the state of Iran’s air defences.

Underscoring the secrecy, Hegseth said the administration notified Congress after the attack. However, a spokesperson for Republican House Speaker Mike Johnson said he was briefed before the strikes.

The US gave no notice to most allies. Even the UK, one of its closest allies, got only a few hours’ notice, according to people familiar with the situation.

The US did, however, co-ordinate with Israel, according to the Israeli government. Israel’s security cabinet also watched the American strikes in real time, according to one person familiar with the matter.  

The US and Israel also engaged in co-ordinated deception ahead of Israel launching its attack on Iran on June 13. Leaks to the Israeli media suggested that Netanyahu and Trump had held a fractious phone call over Iran with Trump pushing for a diplomatic solution, which one person familiar with the call said was an attempt to dupe Tehran.

Additional reporting by Neri Zilber and Lauren Fedor