After weeks of speculation, the US and Israel commenced “major combat operations” in Iran on Saturday.“Our objective is to defend the American people by eliminating imminent threats from the Iranian regime,” US President Donald Trump said in a video shared on social media. He said the immediate objective was “eliminating imminent threats from the Iranian regime.” Israeli Prime Minister Benjamin Netanyahu echoed this messaging, saying the joint attack sought to “remove an existential threat posed” by Iran.In turn, Iran launched a counterattack, sending a wave of missiles and drones targeting Israel. The Associated Press also reported explosions over US military installations in Bahrain, Kuwait and Qatar.The latest round of US-Iran talksThe strikes came amidst renewed negotiations between the US and Iran in February to resolve their differences over Tehran’s nuclear programme. The Trump administration wants Iran to completely discontinue its enrichment of uranium, roll back its long-range missile programme, and end its support for militant groups like Hamas and Hezbollah in the region. Iran, on the other hand, has maintained that it would maintain its nuclear programme for peaceful purposes and that it would only discuss nuclear issues.Trump expressed frustration over the outcome of the latest, and third round of indirect talks at Geneva. “I’m not happy with the fact that they’re not willing to give us what we have to have,” Trump told reporters on Friday. “They cannot have nuclear weapons.”Also Read | Iran nuclear talks were progressing. But US backed Israel’s attack plan, like with Iraq in 2003Trump’s lead negotiator and Middle East envoy Steve Witkoff claimed last week that Iran was “probably a week away from having industry-grade bomb-making material”, a claim rebuffed by independent experts. Iranian President Masoud Pezeshkian said this month that the country was open to “any kind of verification”. However, Iran has restricted access to international inspectors since last June, when the US and Israel conducted a similar joint military operation against Iran.All hope of amicably negotiating a deal was always fraught, considering the US commenced its largest-ever military build-up in West Asia at the end of January. Trump has repeatedly threatened military action to compel Iran to reach a deal amenable to the US, and earlier, to cease its crackdown on country-wide protests.Story continues below this adIn November 2025, Iranian Foreign Minister Abbas Araghchi said that Iran had ceased all “undeclared nuclear enrichment” in the country, ever since the country’s nuclear facilities —and military facilities — were targeted in the 12-day military operation in June.“All of our facilities are under the safeguards and monitoring” of the International Atomic Energy Agency (IAEA), Araghchi then said. “There is no enrichment right now because our facilities, our enrichment facilities, have been attacked.”Enrichment is the process by which the concentration of Uranium-235 (U235) is increased in a sample of natural uranium, which is primarily more than 99 per cent Uranium-238 (U238). U-235 has industrial applicability due to its fissile nature, meaning its nucleus can be broken down (or is fissionable) through a process that produces energy, and is capable of sustaining a chain reaction. A 3-5% enrichment level provides for electricity generation in nuclear power stations. However, highly-enriched uranium (HEU), with concentrations of 90% or more of U235, is required to generate nuclear weapons. Prime Minister Benjamin Netanyahu of Israel, and US President Donald Trump. (The New York Times)Last year’s joint attack by Israel and the US saw the deployment of 30,000-pound bunker-busting bombs targeting Iranian nuclear facilities in Fordow, Natanz and Isfahan, which possess the infrastructure to convert natural uranium into HEU.The sites of Iran’s nuclear programmeStory continues below this adA report by the Institute for Science and International Security (ISIS) in November 2025, co-authored by David Albright, concluded that Iran’s uranium enrichment capacity had been severely degraded, with no current capacity to enrich uranium in any significant quantity or manufacture centrifuges at scale.Nearly a year after the attack, however, Iran appears to have strategically recovered from its losses. Given the extent of damage to enrichment sites, these have been largely untouched. However, sites of weaponisation and storage have been reinforced, with Tehran prioritising their concealment and durability over visible signs of reconstruction. In a post on X, Albright suggested that Iran stood to benefit from stalling its talks with the US, and could create a cover for burying its assets before it agreed to inspections.NUCLEAR ENRICHMENT SITESAll the nuclear enrichment sites are under the authority of the Atomic Energy Organization of Iran (AEOI).1. NATANZ ENRICHMENT COMPLEX: Long regarded as Iran’s main enrichment site, Natanz, located 220 km southeast of Tehran, is home to two enrichment plants that were operational at the start of Israeli attacks in June 2025.Story continues below this adOf these, the Fuel Enrichment Plant (FEP) was a vast underground facility designed to house 50,000 centrifuges, the uranium-enriching machines. It had 17,000 installed centrifuges, of which 13,500 were operational and enriching uranium up to 5% in June. However, the plant’s electricity infrastructure was destroyed in Israeli airstrikes, with the IAEA telling the BBC last June that all operational centrifuges were likely “severely damaged if not destroyed altogether”. The ISIS report confirmed that the site remained destroyed with no repairs or reconstruction for the damage from the bunker-busting GBU-57 bomb.More Explained | Israel, US strike Iran: What it means for oil flow via Strait of Hormuz, what are India’s concernsThe Pilot Fuel Enrichment Plant (PFEP) in Natanz is the smallest Iranian enrichment facility, and is located above ground. It was primarily a research and development (R&D) centre, with much of the R&D work since moved underground to the FEP. The PFEP had two interconnected full-size cascades (interconnected clusters of centrifuges) of up to 164 advanced centrifuges each, and enriched uranium to up to 60%. It also had up to 201 centrifuges enriching up to 2%.The PFEP was destroyed in the Israeli attack on June 13, and no reconstruction activity was noted in the ISIS report.The Pickaxe mountain, known locally as the Kūh-e Kolang Gaz Lā, located south of Natanz, was identified by Tehran as a site for a nuclear facility deep within the mountains. The AP reported that Iran’s stated goal was to fortify its nuclear facility against a possible last-ditch US weapon designed to destroy such sites. This site had not been targeted in June’s airstrikes. As of February, construction on the facility was nearing completion, with its security perimeter wall finished and tunnel entrances being hardened. It is claimed that the facility is being dug at an estimated depth of about 80 to 100 metres under hard granite rock in a bid to secure immunity against the American bunker-busting bomb.Story continues below this ad2. FORDOW ENRICHMENT SITE: The major share of uranium enrichment had occurred at a site buried deep within a huge mountain at Fordow, nearly 190 km southwest of Tehran. The facility is completely underground. UN inspectors in 2012 reported the presence of tunnels with thick walls and blast-proof doors, with some bunkers protected by 300 feet of rock, according to a report in The Washington Post.According to the IAEA, the country’s most powerful centrifuges were located here. Fordow had about 2,000 operational centrifuges, but used roughly the same number as the PFEP did.This site produced uranium enriched up to 60%, a small step away from weapons-grade levels of 90% enrichment. In the most recent quarter, 166.6 kg of uranium enriched to up to 60% were produced, which, if enriched further, could be used to produce about four nuclear weapons, according to an IAEA yardstick.The site faced no damage from Israeli airstrikes, whereas US strikes damaged its ventilation shafts during the June conflict. As of November, the site remained dormant, with craters filled in and tunnel entrances backfilled.Story continues below this ad3. ISFAHAN: Iran’s nuclear complex at Isfahan, located 350 km southeast of Tehran, is home to three Chinese research reactors and labs under the Iranian atomic programme.The IAEA said that Israeli strikes on June 14 had damaged four buildings at this complex. This included the Uranium Conversion Facility (UCF), where ‘yellowcake’ uranium is turned into uranium hexafluoride, the raw input for centrifuges, so that it can be enriched. As of November, the UCF remained destroyed, with no signs of reconstruction.The underground tunnel complex at the site was reportedly targeted by US Tomahawk missiles. The ISIS report assessed this complex as holding large amounts of Iran’s stock of 60% HEU, or a total of 440 kg, as estimated by the IAEA. A Reuters report in February noted that all three tunnel entrances to the complex were completely backfilled with soil, which ISIS interpreted as hardening against airstrikes and a potential special forces raid.A CNN analysis from last week showed that damaged structures had been rebuilt at the 7th of Tir Industrial Complex near Isfahan, linked to producing centrifuge parts for uranium enrichment.The complex was sanctioned by the UN in October 2025.Story continues below this ad4. KARAJ: Karaj, located 42 km northwest of Tehran, houses two enrichment sites: TABA (Towlid Abzar Boreshi Iran) and TESA (Iran Centrifuge Technology Company). Both facilities manufacture centrifuge components for uranium enrichment, alongside the UN-sanctioned Kalaye Electric Company (KEC), located in eastern Tehran. (The KEC was struck and destroyed in the June conflict.)According to the November ISIS report, both sites had been destroyed, with minimal cleanup.NUCLEAR WEAPONISATION SITES:The country’s weaponisation sites are under the authority of the sanctioned Organization of Defensive Innovation and Research (SPND), described by ISIS as a military advanced research and development entity that reports directly to the highest levels of the military and the Ayatollah.* Sanjarian in Tehran was reportedly a key site associated with the historical “Amad Plan,” Iran’s past crash program to develop nuclear weapons. The site was associated with the development and testing of the “shock wave generator”, exploding bridgewires and associated parts. The November ISIS report showed that the site, targeted in June’s strikes, was heavily damaged.Story continues below this adAlso Read | Iran conflict: How many military bases does the US have in the Middle East, and where* The Mojdeh site, also called Lavisan II, in northern Tehran was the former headquarters of the SPND. It was bombed twice by Israel on June 18. As of November, an active sanitisation process was underway, with buildings demolished and rubble cleared. The ISIS assessed this as an effort to clear evidence of past nuclear work before future inspections.The new headquarters of the SPND, located about a kilometre away from the old HQ, was also reportedly being demolished for similar reasons, the ISIS report said.* The Shahid Meysami Research Centre, located west of Tehran, was also targeted in the June attacks. The site is believed to be a component of SPND and Iran’s chemical weapons programme. Israeli intelligence believed it to have housed “plastic explosives and advanced material for nuclear detonation testing.” The ISIS report said that Iran had cleaned up several damaged buildings, as a “possible prelude to rebuilding” the centre.OTHER SITES:* As of February, construction was underway at the Taleghan 2 nuclear facility at the Parchin military complex southeast of Tehran. Satellite images accessed by ISIS showed that Iran had built a concrete structure believed to be blast-resistant and had encased it with soil. As of February 16, the facility had vanished completely from satellite view, Reuters reported.* The missile bases at Shiraz South — one of 25 primary bases capable of launching medium-range ballistic missiles — and Qom were both targeted by Israeli airstrikes in June. The facilities at both sites were being repaired but had yet to return to their full capacity as of February.* Bushehr province, located along the Persian Gulf and 750 km south of Tehran, houses Iran’s lone commercial nuclear power plant, dating back to the mid-1970s. Iran has been building two more reactors at the site, with uranium produced in Russia and monitored by the IAEA.The site was not targeted in Israeli airstrikes, and work has continued amidst continued sanctions from the West.The province is also home to the world’s largest natural gas field. The South Pars gas field, which Iran shares with Qatar, was targeted by Israeli strikes on June 14, causing a partial suspension of production.* The Arak heavy water reactor, also called Khondab, is located 250 km southwest of Tehran. According to AP reporting, it presents an alternative path to a nuclear bomb, as the heavy water used to cool nuclear reactors also produces plutonium as a byproduct, which can potentially be used in nuclear weapons. The report said that Iran agreed under the 2015 nuclear deal with world powers to redesign the facility to relieve proliferation concerns — an obligation Iran secretly did not fulfil.Israeli airstrikes damaged the reactor containment building in a direct hit, as well as distillation towers at the adjacent heavy water production plant. The November ISIS report only noted the reconstruction of the water plant, which it did not consider a reconstruction of nuclear weapons capabilities.