The uranium enrichment plant in Natanz is located halfway between the cities of Isfahan and Kashan. The only things visible from the highway are warehouses and workshops. Most of the plant is buried in tunnels, well over 60 meters below the surface – difficult to destroy even with the most powerful American bunker-busting bombs, it is said.

It is almost impossible to see what is happening underground here from the outside. What is known is that this is the site where Iran is further developing its nuclear program, which the international community had hoped to end using diplomatic means – and which Israel and many of Iran's Arab neighbors feel threatened by.

This is truer than ever following Iran's attack on Israel in the night of April 14, when the regime in Tehran launched a salvo of more than 300 drones, rockets and ballistic missiles in the country's direction.

Outside of Israeli security circles, no one knows exactly what possible targets in Iran the military planners are currently discussing in the event that war with Iran does indeed break out one day. But it is likely that, in addition to military bases, airports and oil facilities, the locations of the nuclear program will also be considered.

Around 170 kilometers north of Natanz, between Tehran and Qom, the city that is the world's largest center of Shiite scholarship, is the Fordo nuclear facility, also hidden underground. Some 150 kilometers further to the west, near the industrial city of Arak, there is another nuclear facility with a research reactor and a heavy water reactor.

An Israeli military strike against the Iranian nuclear program is the maximum variant of retaliation that is currently conceivable. It would be a bold move, feasible, if at all, only with the help of the United Sates – and with incalculable consequences for the rest of the world.

The danger of a major war in the Middle East is currently greater than ever. And the risk remains just as high now that Israel apparently responded with a limited strike early on Friday morning.

It still isn't entirely clear what happened. According to Iranian reports, there were several explosions near the city of Isfahan in central Iran. Reports from the U.S. media, which cite unnamed Israeli and Iranian sources, indicated that it could have been an attack involving drones, possibly near an air force base. Iran initially played the incident down. It also remained unclear whether Israel would follow up with further strikes – or whether Iran would react once again.

The New York Times reported that four options had been discussed in Israel in the preceding days: a strike against an Iranian facility outside Iran, such as a Revolutionary Guard base in Syria; an attack on a "symbolic target" inside Iran; a cyberattack on the country's infrastructure – and an intensification of acts of sabotage or targeted killings inside Iran, of the type Israel's foreign intelligence service has allegedly been carrying out for years.

Reports coming out of Isfahan point to the second option. And it does seem fitting given that in military retaliation operations, states are usually keen to "thematically link" the counterstrike, as Fabian Hinz of the think tank International Institute for Strategic Studies (IISS) puts it. To strike a specific unit or base that they believe to be responsible for the original attack, for example. That concept is at least one common denominator shared by countries as different and hostile as Israel and Iran.

Ever since the Hamas terror attack on Israel on October 7 and the war in Gaza, there has been an increased possibility of a broader war pitting Israel, the U.S. and their allies against Iran and its proxy forces in Lebanon, Iraq, Syria and Yemen. But despite the fact that Iran has co-financed the Palestinian terrorist organization Hamas, or that Israel is involved in battles with the Iranian-backed Hezbollah or that Houthi militias allied with Iran are launching drones from Yemen towards Israel, a larger conflagration has yet to be sparked.

It would be a war that could set the entire region between the Levant and the Hindukush on fire. "A war with Iran could destroy emirates such as Abu Dhabi or Dubai within 24 hours," the American Iran expert Vali Nasr said in an interview with DER SPIEGEL. Such a war could jeopardize global oil supplies, disrupt international trade and strengthen Russia and China.

It is a war that few people want. But wars don't always arise because someone decides to start them, sometimes they are the result of events that develop a momentum that no one can escape. Sometimes it is overreactions or miscalculations that set off a spiral of escalation.

What is the history of the current crisis?

On the night of April 14, an event occurred that had the potential to start a major war: It was Iran's first direct military attack on Israel. Iran's regime launched a massive airstrike with more than 300 drones, cruise missiles and ballistic missiles. The Shahed drones flew west for hours. It didn't take long to detect them, but it was nonetheless an attempt to demonstrate military power.

None of the drones and very few missiles reached their targets. Most had been shot down by Israel, the U.S. or their allies before they reached Israeli airspace, even by neighboring Arab country Jordan. Israel's missile defense took care of most of the rest. Considering the scale of the attack, the civilian and military damage was minor. The only victim known by name: a seven-year-old Bedouin girl in the Negev desert who was injured.

The geopolitical consequences, however, are enormous. For the first time in the decades-long shadow war between the two hostile countries, both have now attacked the other from their own territory. The former Iranian ambassador to Lebanon, Ahmad Dastmalchian spoke of a "paradigm shift" in Iran's "defense policy." "Now, at the latest, Iran has passed the point of no return," said Michael Roth, the chair of the Foreign Policy Committee in the Bundestag, Germany's federal parliament.

But the Iranian attack wasn't the first cross-border assault in this conflict. An Iranian consulate and residence building in Syria's capital city Damascus was destroyed in an April 1 airstrike, presumably by Israel. Sixteen people, including Iranian Brigadier General Mohammad Reza Zahedi, and other high-ranking officers and civilians were killed. Attacks on diplomatic missions are considered to be taboo by the international community, but for Iran, it was a public humiliation. As usual, Israel did not claim responsibility for the attack, but also made no effort to deny it.

That's how the logic of strike and counterstrike began. After Iran's attack last weekend, Israeli Army Spokesman Daniel Hagari said on Tuesday: "We cannot stand still from this kind of aggression." Iran will not "get off scot-free."

In the event the Israelis struck, the regime in Iran said it would strike back. And that this retaliation would be "much more serious" than the attack on April 13, an adviser to Iranian President Ebrahim Rasi said. If Israel "makes another mistake," said Deputy Foreign Minister Ali Bagheri, the country "will not have 12 days, a day or hours. The next strike will take place within seconds and has already been approved."

And even if the Israeli reaction now appears to have been rather mild and Iran has so far shown no signs of a renewed counter-reaction: The conflict between Israel and Iran is now being played out openly. The shadow war is no longer in the shadows. And the danger remains great that the conflict will escalate further – if not now, then in the coming weeks, months or years.

Israel's path to this escalation is closely linked to one name: Prime Minister Benjamin Netanyahu and the rise of the political right.

But how did Iran, the major Shiite power in the Middle East, become Israel's archenemy? Is there a way to slow down this extreme confrontation, which threatens to erupt into an open, and possibly one day nuclear, war? The question lingering over everything is this: How can Iran still be prevented from building a nuclear bomb?

At what point could Iran have a nuclear bomb?

When asked whether Iran was already capable of building a bomb, the former head of the Iranian nuclear authority, Ali Akbar Salehi, recently replied in a television interview: "Imagine what a car needs; it needs a chassis, an engine, a steering wheel, a gearbox. You're asking if we've made the gearbox, I say yes. Have we made the engine? Yes."

The physicist and weapons expert David Albright, a former inspector with the International Atomic Energy Agency (IAEA), puts it more precisely. According to his estimate, Iran needs around six months to produce what is called a "crude" bomb that could be carried on a ballistic missile. However, this would require a decision from Revolutionary Leader Khamenei to lift the ban he imposed in 2003 on the production of nuclear weapons and weapons of mass destruction. A growing number of voices are now urging Khamenei to do precisely that. But so far, according to Albright, this decision apparently has not yet been made.

For a long time, it appeared that Iran could be dissuaded from building a bomb through diplomatic means: In 2015, the regime, which was ruled by a reform-oriented president at the time, concluded an agreement with the backing of the U.S., the European Union, Russia, China, France, the United Kingdom and Germany. The so-called Joint Comprehensive Plan of Action (JCPOA), known as the Iran deal, called for Tehran to forfeit 97 percent of its low-enriched uranium. The stockpile of enriched uranium was to be exported almost entirely to Russia.

All of this took place in a different, more hopeful world: The West, Russia and China were still working together back then. In the meantime, the geopolitical situation has changed considerably. China and Russia are now firmly on Iran's side against the American-led world order. At a recent crisis meeting on Iran involving the U.S. and other countries, China and Russia were not even present.

Hardliners on all sides always wanted to torpedo the Iran deal: in Israel, the forces around Benjamin Netanyahu, the conservatives in Iran – and right-wing Republicans in the U.S. The main argument against the deal was that it didn't include Iran's missile program or its aggressive proxy forces in the Middle East. Proponents of the deal believed that they would be able to negotiate these issues in the next steps. But in 2018, U.S. President Donald Trump withdrew his country from the deal. His successor Joe Biden has tried to revive it, but those efforts have so far been in vain.

The International Atomic Energy Agency still has access to Iran's nuclear facilities, but entry has been severely restricted since the termination of the deal. "In the current chaos in the Middle East, they could try to use an excuse to deny the inspectors access to the enrichment facilities for a few days, as they did on the day of the drone attack on Israel," says former inspector Albright. It's not very difficult to increase the enrichment from 60 to 90 percent, meaning the amount needed for producing weapons-grade material.

Albright believes it is possible that Khamenei will reverse his decision "if the survival of the nation is at stake. They are so close that this alone could make it tempting to build the bomb. Still, the Iranians will have to weigh up what that means" – a likely war with Israel and possibly also with the U.S.

Conversely, Israel and the U.S. would also have to ask themselves what Iran's renewed response might look like. In any case, Israel has only limited possibilities for destroying Iran's nuclear program. "I think it is more likely that Israel will give a response that strengthens its deterrent but does not challenge Iran to a major attack."

Why were protests by women unable to topple the regime?

In the West, we have recently heard almost exclusively about protests in Iran: about the women in Tehran and other cities who threw off their headscarves a year and a half ago, about demonstrations in Kurdistan and Baluchistan, where participants were repeatedly killed with targeted shots.

The protests didn’t topple the regime, but they did demonstrate how great is the chasm between large segments of the population and the country’s rulers. Most Iranians don’t think much of the regime, and many don’t consider themselves to be in a conflict with Israel. At the same time, however, a faction of ultra-hardliners has developed in recent years – in parliament, among the clerics and among commanders of the Revolutionary Guards – called Jebhe-ye Paydari, or the Front of the Stability of the Islamic Revolution. And for them, the leadership of the aging Khamenei is too lax.

Instead of compromise, this group is demanding toughness, born out of a messianic tradition. The Front of the Stability of the Islamic Revolution, the Economist recently wrote, "are to Iran what the religious hard right are to Israel."

Step by step, these extremists are pushing the pragmatists out of the country’s circles of power. They are even enforcing the hated hijab requirement for women once again: On the day of the Iranian air attacks on Israel, the regime once again sent the morality police into the streets. And these hardliners are upping the pressure to transform the anti-Israeli and anti-Western propaganda into a real military conflict. Faced with the decision between losing face or getting Iran involved in a large war in the Middle East, they tend to favor the latter.

Where did the animosity between Iran and Israel come from?

The acrimony between the two countries is not rooted in a long, bellicose history. It began as a propaganda project of the Iranian Revolution, which put an end to the country’s monarchy in 1978-79.

Under Shah Mohammad Reza Pahlavi, Iran became one of the first countries to recognize Israel in 1948. The secret services of the two countries cooperated, and both states were united by their distance to their Arab neighbors. The young country of Israel helped Iran develop its agricultural sector and bought oil from the country.

Historian David Menashri, 79, was born as the son of Jewish parents in Tehran before emigrating with his parents to Israel, but he also spent several years in Iran in the 1970s. At that time, he says, the two countries had a relationship "like a marriage without a license" – a rapport that was shaped by religion from the very beginning. On the one hand, both countries considered themselves to be "chosen by God" by virtue of their long histories, says Menashri. But on the other, anti-Semitism had a long history in Iran.

There was, for example, a rule according to which Iranian Jews were not allowed to leave their homes when it was raining, because they were considered najis, ritually unclean, and water dripping off of them would allegedly impurify the streets. The shah, says Menashri, knew that he couldn’t be particularly open about his ties with the Israelis. The Israeli Embassy in Tehran did not fly the country’s flag and while the airline El Al had daily flights to the Iranian capital, those flights were not publicly displayed at Mehrabad Airport.

It was revolutionary leader Ruhollah Khomeini who declared Israel to be "Little Satan." The designation "Great Satan” was reserved for the U.S., which had provided the shah with military support for years. Kohmeini accused Israel of being an "enemy of Islam" and declared an annual Al-Quds Day, calling for the liberation of Jerusalem – though during the Iran-Iraq War (1980-1988), Khomeini had no compunctions about importing arms from Israel through secret channels. Israel’s leadership likewise kept open the possibility of resuming closer cooperation with Iran at some point in the future. For Khomeini, the Jewish state was a useful tool for whipping up the fervor of his followers. "If Israel hadn’t existed," says David Menashri, "his regime would have had to invent it."

Indeed, one reason Iranian propaganda later targeted Israel and the U.S. was because it so accurately reflected the mood on the streets of Arab countries, with which Iran was at odds and whose leaders were generally allied with the U.S.

Who actually rules Iran?

The Iranian regime is stable primarily due to its unique construction. Standing over everything is the country’s religious leader, Ali Khamenei.

In 1979, revolutionary leader Khomeini established the Pasdaran, the Revolutionary Guards, as a protective force against the country’s regular army, who Khomeini suspected of being disloyal.

Today, the Pasdaran, with almost 350,000 men, is the most powerful military force in Iran and has its own ground, air and naval forces in addition to an arsenal of missiles. The country’s nuclear program is also part of its portfolio as is the large Basij militia, which keeps close tabs on schools, universities, factories and official agencies to ensure that no opposition is allowed to develop.

The Revolutionary Guards are not under the control of the country’s elected president or the parliament, instead answering only to Supreme Leader Ali Khamenei, who took charge when Khomeini died in 1989. He holds vastly more power than President Ebrahim Raisi, though the president is also considered to be a Khamenei ally.

The Pasdaran has become the gravitational center of the Iranian state. In addition to its military strength, it also has gigantic holdings through which it dominates every sector of the Iranian economy, including banks, construction companies, supermarket chains, oil refineries, airports, luxury hotels, eye clinics and newspapers.

But as sprawling as its economic empire is, the Pasadaran keeps its influence largely under wraps. Estimates as to the group’s contribution to Iran’s gross social product vary between one-third and two-thirds. General strikes of the kind that toppled the monarchy in 1978-79 become difficult when the regime also controls a majority of the economy.

Why is Iran spreading its influence across the Middle East?

From the very beginning, Khomeini’s Islamic Republic was anything but a peaceful state. But instead of seeing today’s archrival Israel as its biggest enemy, the focus was more on countries like Iraq, Egypt and Saudi Arabia, all of which the regime saw as rivals for the political, religious and economic dominance of the Middle East. To secure Iran’s influence in the region, the foreign, elite branch of the Pasdaran, the Al-Quds Brigades, was founded in 1988, named for the Arabic word for Jerusalem.

In the late 1990s, a man named Qassem Soleimani – a largely unknown officer at the time – took over control of the Al-Quds force. Marked by the horrors of the Iran-Iraq conflict, Soleimani set about building something new – a hybrid army made up of other nationalities but which would remain under his control. Soleimani was from the mountains of southern Iran, was fluent in the unwritten rules of the tribes, had experience as a wartime commander, exuded charisma and spoke perfect Arabic.

Over the course of several years, he discreetly built up a shadow army over which the Iranians had full control, but which didn’t involve Iranians themselves fighting and dying. His model foresaw providing financial and military support to fellow Shiites in other countries, religiously indoctrinating them and then deploying them as bridgeheads in the Arab world. The blueprint was the Hezbollah militia in Lebanon. Israel marched into the country in 1982 in order to drive out the leadership of the Palestinian Liberation Organization (PLO). In spring 2000, the Israelis withdrew, and Hezbollah posed as the country’s liberators.

Three years later, in 2003, a golden opportunity arose for Iran to expand its power: The U.S.-led invasion of Iraq and the toppling of Saddam Hussein, the country’s dictator. The majority of Iraqis are Shiites, and it didn’t take Iran long to fill the power vacuum. A growing number of militias were trained by Soleimani’s men.

The 2011 uprising in Syria as part of the Arab Spring provided the next opportunity. The Assad-family dictatorship in Damascus was Iran’s only Arab ally – and it couldn’t be allowed to fall. Indeed, Syria became the ultimate proving grounds for Soleimani’s creation. As of 2014, Iraqis began fighting at division strength in the region surrounding the Syrian capital of Aleppo, led by Hezbollah officers from Lebanon. Shiites from Afghanistan, Pakistan and Yemen served as cannon fodder for the front lines. And Iran was pulling the strings.

General David Petraeus, who led the U.S. forces in Iraq in 2008, received what he says was a secret message at the time: "General Petraeus, you should know that I, Qassem Suleimani, control the policy for Iran with respect to Iraq, Lebanon, Gaza and Afghanistan." It wasn’t bragging, it was just the truth.

Because Soleimani’s troops didn’t just battle it out with local forces, but increasingly with U.S. units as well, then-U.S. President Donald Trump made a far-reaching decision in January 2020: He had General Soleimani killed at the Baghdad airport using Hellfire missiles. Iran still hasn’t completely recovered from the loss, with Soleimani’s successor lacking his stature. But many of the militias once controlled by Soleimani still exist – and some, such as the Houthis in Yemen, have even grown stronger. "Their proximity to Iran gives them power over their competitors," says Middle East expert Charles Lister of the Middle East Institute in Washington. "Then: the weapon systems, suicide drones, missiles, plus the training effects. It's the complete package. It is truly a network, fascinating. Each of them operates in their own environment. They are part and parcel of a regional network."

Iran reacted to the assassination of Soleimani by firing missiles at U.S. military bases. But the response was far more modest than the attack unleashed on Israel following the killing of its generals in Damascus.

Why didn’t Iran’s allies launch attacks after October 7?

Many Western observers were surprised that Tehran and Hezbollah clearly held back following the Hamas terror attack on Israel on October 7, 2023. In truth, however, such reserve has not been uncommon in recent decades. Despite all the propaganda against the "Zionist entity," Soleimani’s successor in recent years has reportedly argued internally against provocations of Israel. Tehran may support Hezbollah, Hamas and the Islamic Jihad, all of which are enemies of Israel, but control over Arab countries has always been more important to Tehran.

According to U.S. intelligence, Hamas launched the October 7 attack on its own and hoped that Hezbollah and Iran would join the war they started.

But that was never their intention, and now – after years of bellicose anti-Israeli and anti-Western propaganda – the Iranians found themselves facing a dilemma. That has been readily apparent by Hezbollah’s attempts since October 7 to lead a limited war across the Israeli border.

Revolutionary leader Ali Khamenei, recalls Israeli Iran expert Raz Zimmt of the Institute for National Security Studies (INSS), a think tank in Tel Aviv, once said that Iran occasionally had to operate "like a boxer" and take punches if it served to achieve larger strategic aims.

What next?

The recent escalation between Iran and Israel – one which appears to have brought the Middle East closer than ever to a large conflict – was apparently the product of a far-reaching misjudgment three weeks ago. Israel’s government and security services came to the conclusion ahead of their April 1 airstrike on the Iranian consulate in Damascus that the leadership in Tehran would react to this strike with a relatively moderate response – as had been the case following a series of similar attacks in recent months.

Even though the Israelis had previously killed more than a dozen pro-Iran militia leaders in Syria and Lebanon, the attack on the consulate in Damascus "crossed a red line,” says Zimmt. "Apparently those responsible hadn’t registered that the Iranians could not accept the killing of such senior commanders, particularly at this place."

An extensive New York Times report confirmed that not only did the Israelis fail to coordinate with their allies in Washington ahead of the attack in Damascus, they also underestimated the fact "that the unwritten rules of engagement in the long-simmering conflict between Israel and Iran have changed drastically in recent months.”