two countries on the threshold of a nuclear bomb

A secret nuclear programme deep underground, shielded from American eyes, slowly revealing the secrets of the atom — and disgorging the fuel for an atomic bomb. Enemies closing in, the drumbeats of war growing louder.

And then, on the eve of conflict, a hasty decision to pull together at least one rudimentary nuclear device. If the nation faced annihilation, maybe an atomic explosion — its mushroom cloud seen by the world — could save it?

This was Israel in 1967, when historians now understand that the Jewish state first inched to the edge of the nuclear threshold. It stopped short of the last resort, a demonstration test of a crude bomb, which its unexpected victory in the six-day war rendered unnecessary.

But the story is not so different from that of Iran in the months leading up to what US President Donald Trump has now dubbed the 12-day war — watching Israel debilitate the Islamic Republic’s allies, from Hizbollah in Lebanon to devastating the Syrian military after Islamist rebels toppled the Assad regime.

Now, with Israel threatening more violence if Iran rebuilds its enrichment capacity, the Islamic Republic faces the same question Israel had to confront in 1967: to create a measure of final deterrence by sprinting to a nuclear weaponor step back from the brink?

“Iran is now in the midst of a long-running, serious internal debate. It’s the do-or-die moment,” said Vali Nasr, former senior adviser to the US state department and author of Iran’s Grand Strategy. “It’s also paradoxical that Israel is pushing Iran to make that same decision that they made.”

The six-day war changed the course of the Middle Eastwith Israel’s surprise victory over its larger neighbours and the capture and occupation of the West Bank and Gaza. It also transformed a young Israel, and its ambiguous relationship with weapons of mass destruction, into a unique — if completely opaque — nuclear power, its dozens of devices both undeclared and undisputed.

The west’s toleration of Israel’s secret arsenal, estimated by the Federation of American Scientists at just under 100 sophisticated weapons, is seen in the Middle East as a symbol of its hypocrisy, allowing an ally to flout non-proliferation norms while punishing Iran, which has in many respects complied with its treaty obligations.

But Israel’s unique status is not just the result of its strategic alliance with the US. It was the product of a different historical period, when the Jewish state was younger and weaker, its enemies stronger and determined to wipe it off the map. The secret 1969 deal with the US, which allowed Israel to keep its nuclear weapons undeclared, reflected how Israeli leaders turned their country’s precarious position — so soon after the Holocaust — into an extraordinary exemption no other state received.

If Iran were to lurch towards a nuclear weapon now, however, it would present world powers with an impossible choice — accept a new, brash entrant to the nuclear club, tempting others to follow suit, or seek to punish it like North Korea.

The third option, to reap the political benefits of stepping back from the nuclear threshold, remains on the table.

Avner Cohen, a leading historian of Israel’s nuclear secrets, said the Middle East had been brought to this moment by Iran’s emulation of a young Israel: operating a nuclear programme that was partly open, partly clandestine, “having a closer and closer proximity to the bomb” but delaying any final decision until absolutely necessary.

“Iran wanted very much to be another Israel, to follow in Israel’s path,” said Cohen, a professor at the Middlebury Institute of International Studies in Monterey, California. He pointed to how Israel built up broad expertise that would enable the creation of a nuclear device at a time of crisis — without ever having explicitly chosen that path.

“Iran wanted, and in many ways were imitating, the opaque Israeli mode of operation but their political circumstances were different — and more adversarial,” he said, referring to Israel’s 1969 deal with the US to keep its arsenal secret.

“In the end, the world has been much more friendly to Israel, and less forgiving of the Iranians.”

It took four and a half decades for Israel and Iran’s regional rivalry to boil into direct conflict, during which Iran’s leaders embedded the destruction of the “Zionist entity” deep into the Republic’s political discourse.

For Israel, Iran’s growing military prowess since the turn of the century, nuclear programme and well-funded proxies were increasingly viewed as an existential threat.

For Iran, Israel emerged more suddenly as a threat on an existential level: Israeli leaders speak openly about regime change in Tehran, and its military has already demonstrated it can wreak damage across all of Iran at will.

Unlike Israel, which succeeded in hiding its nuclear ambitions even from close allies, Iran has inched closer to the technical capabilities of a bomb after signing the non-proliferation treaty and enduring onerous inspections while swearing off using nuclear weapons — the Ayatollah Ali Khamenei branded their use haram in the early 2000s.

And until Israel and the US attacked Iran’s nuclear programme, western intelligence assessments chimed with the UN’s view that Iran had not formally decided to pursue a nuclear weapon.

For Israel, impending conflict in 1967 put paid to any doubts among policymakers. Historical records show Prime Minister Levi Eshkol musing to colleagues about “a certain weapon”, while military chief Yitzhak Rabin worried about a surprise attack on Israel’s only nuclear reactor, which he warned had “a lack of international legitimacy”.

In Iran last year, as conflict with Israel was brewing, policymakers began issuing ambiguous warnings that Tehran could consider changing its nuclear doctrine.

Months after Israel and Iran’s first volley of strikes in April 2024, Kamal Kharrazi, foreign affairs adviser to Ayatollah Ali Khamenei, told the Financial Times that “we are not for building nuclear weapons” but that if Iran faced an existential threat, “naturally we [would] have to change our doctrine”.

In February last year, the former chief of the Atomic Energy Organization of Iran, Ali-Akbar Salehi, had said that Iran’s sprawling nuclear research programme had resulted in vast technical expertise.

“What does a car need? It needs a chassis, an engine, a steering wheel, a gearbox,” he said when asked whether Iran could build a nuclear weapon. “You’re asking if we’ve made the gearbox, I say yes. Have we made the engine? Yes, but each one serves its own purpose.”

In the lead-up to Israel’s 1967 war, research carried out by various parts of the government had resulted in the knowledge and even the fuel needed for a nuclear device, but there is no publicly available evidence that its leaders had explicitly ordered the construction of a bomb until shortly before the conflict.

On Iran’s part, as conflict with Israel grew more likely in recent months, there was one major shift: it doubled its stockpile of uranium enriched to 60 per cent purity — far beyond what is needed for nuclear energy — to about 400kg.

That stockpile could in theory be quickly enriched to weapons grade. But any implosion device Iran could fit it into would be a crude, if effective, prototype — far from a sophisticated weapon.

In Israel, it was just such a prototype that nuclear scientists hastily assembled and handed over to soldiers in 1967, according to research by Cohen, including an interview with the military official in charge of what became known as “The Samson Option”.

That product emerged from research and subterfuge, including at the Negev Nuclear Research Center at Dimona in the late 1950s, where Israel built a secret underground facility for processing plutonium.

Around that time, Israel’s security concerns did not involve Iran. The Shah, an ally of Washington, had received a nuclear reactor in 1967 as a gift from the US under an Eisenhower-era programme, Atoms For Peace. A year later he signed the NPT.

By the time of the Islamic Revolution in 1979, when the Shah was toppled, Iran’s nuclear research was rudimentary, and after the revolution most nuclear physicists left the country.

Around the same time, the US assembled a group of scientists to study two flashes picked up in 1979 by an ageing satellite. A few months later, President Jimmy Carter wrote in his diary that “we have a growing belief among our scientists that the Israelis did indeed conduct a nuclear test explosion in the ocean near the southern end of Africa”.

Around then, Israel made a policy decision that remained unchanged, said Uzi Arad, former research director at Israel’s spy agency Mossad. That was the Begin Doctrine: if a belligerent neighbour’s nuclear knowledge was deemed a threat, Israeli war planes would attack.

“The nucleus of Israel’s approach to proliferation has always been this: first, if and when a nuclear programme becomes a threat to Israel . . . it would exhaust all other means to stopping it,” he said. “Then, it would fall back on an air strike.”

So in 1981, Israel attacked a nuclear reactor in Iraq. In 2007, it hit a North Korean-supplied secret reactor under construction in Syria. “And now you have in 2025 Israeli warplanes flying over Natanz and Fordow and Isfahan [in Iran],” he said.

That partly shaped Iran’s own nuclear posture, which ebbed and flowed with geopolitics. In the 1980s, after its war with Iraq, Iran began exploring a nuclear programme to prevent another conflict with its neighbour, said Nasr, but the first Gulf war rendered this threat irrelevant.

A Pakistani nuclear scientist confessed in 2004 to selling older centrifuge technology to Iran in the 1990s, seen by many as the genesis of Iran’s enrichment experiments. And in 2003, after watching the US invade Iraq in the hunt for weapons of mass destruction, Iran declared and shelved a secret programme, called Amad, which the UN watchdog said had been researching — but not building — nuclear weapons.

The focus on enrichment remained, said Nasr. “The Iranians saw an interest in actually, for a very long period of time, in using their programme as a way to bring the US to the table and get the US to agree to lift sanctions,” he said. “They understood there’s no other issue that will bring the US to negotiations.”

Its leaders have constantly maintained Iran was exercising its legal right as a signatory of the non proliferation treaty to have a peaceful nuclear energy programme, and have allowed inspectors into declared facilities, even for surprise visits.

But they also built new, secret enrichment facilities in Natanz, revealed by whistleblowers in 2002, and then at Fordow, a site discovered by western intelligence agencies in 2008. Inspectors from the UN nuclear watchdog were subsequently allowed to visit, including in the days just before Israel launched its surprise attack.

Now those facilities have been damaged, alongside much of Iran’s conventional deterrence. Proxy militias that surrounded Israel with a “ring of fire” have been significantly weakened. Many missile launchers and aerial defences have been destroyed. That leaves Iran with a dilemma as it sits on the edge of becoming a nuclear-armed power.

On building a weapon, “Iran is still doing the cost-benefit analysis,” said Nasr, referring to negotiations with the Europeans and the US. “And right now, perhaps the debate has swung much more in the direction of those who say just do the bomb.

“But the door is not completely shut. The only way you’re going to divert the trajectory that Iran is on is to put a deal on the table that is compelling enough and is resilient enough to influence this debate in Iran.”