Why Israel Can’t Touch the Core of Iran’s Nuclear Program: Over 10,000 Metres of Fortifications Installed

In the aftermath of Israel’s launch of large scale air attacks on Iran on June 13, the possibility of the Israeli Air Force’s continuing attacks causing serious damage to Iran’s nuclear infrastructure has gained growing attention from defence analysts. Although the large majority of Israeli fighters, namely its F-15s and F-16s, have relied on launching cruise and ballistic missiles into Iran from long ranges, the country’s small <a href="https://militarywatchmagazine.com/article/custom-built-specifically-war-iran-modified-israel-f35i" target="_blank">fleet of approximately 40 F-35s</a> has been used for penetration strikes, allowing high diameter bombs with advanced penetrative capabilities to target hardened targets in Iran. Nevertheless, the small number of F-35s available, and the very limited number of bombs the relatively small aircraft can carry, primarily due to the need to house ordinance internally to maintain their stealth capabilities, has limited the fleet’s ability to strike hardened targets. Penetration flights deep into Iranian airspace have also placed the aircraft at considerable risk, and while their advanced stealth, electronic warfare and electronic intelligence capabilities have almost certainly seriously limited losses, Iranian government sources have still <a href="https://militarywatchmagazine.com/article/iran-claims-shootdown-fourth-israeli-f35-deep" target="_blank">claimed to have shot down</a> four of the aircraft and captured two pilots – a possibility which is <a href="https://militarywatchmagazine.com/article/two-israeli-f35-shot-down-iran-pilot-captured" target="_blank">far from incredible</a> when considering the <a href="https://militarywatchmagazine.com/article/iran-top-air-defence-bavar373-f35-shootdowns" target="_blank">capabilities of Iranian air defences</a> and the high risk nature of the operations.&nbsp;<img src="https://militarywatchmagazine.com/m/articles/2025/06/19/article_6853bdfc59c620_17140446.jpeg" title="Natanz Nuclear Facility After Israeli Strikes on June 13">While Iranian air defences continue to <a href="https://militarywatchmagazine.com/article/iran-is-guarded-by-the-world-s-largest-network-of-s-200-long-range-missile-defences-can-it-keep-israeli-fighters-at-bay" target="_blank">pose a challenge </a>to Israeli efforts to drop high diameter penetrative ordinance onto well defended facilities, the extent to which Iran’s nuclear sites have been hardened has left the Israeli Air Force’s ability to seriously threaten them in question. Following strikes on the less well fortified Natanz nuclear facility on June 13, it was reported that major underground infrastructure there had <a href="https://www.theguardian.com/world/2025/jun/16/iran-nuclear-sites-natanz-isfahan-fordow-israel-attack" target="_blank">not suffered serious damage</a>. Despite initial reports that the nuclear fuel enrichment facility in Fordow and the heavy water plant in Arak had been hit on June 13, it was subsequently confirmed that no attacks had been launched on either of them. This could largely be explained by extent of the fortifications at these facilities, with those at the Fordow facility in particular having few rivals in the world. Fordow has long been a leading site for uranium enrichment, while its key infrastructure is estimated to be buried approximately 80 meters underground, far beyond the reach of F-35 attacks.&nbsp;This has for over a decade been seen as a leading complication to possible Western or Israeli plans to attack Iran’s nuclear infrastructure.&nbsp;<img src="https://militarywatchmagazine.com/m/articles/2025/06/19/article_6853be27e10215_67108862.webp" title="U.S. Air Force GBU-57 Bomb">The hardening and heavy reinforcement of the Fordow uranium enrichment plant was done with considerable support from North Korea in the early 2000s, with such fortifications having been a leading area of expertise for the Korean People’s Army since the 1950s. North Korean experts had by the mid-2010s reportedly overseen the construction of over ten thousand meters of nuclear infrastructure and underground facilities for Iran, which reportedly include reinforced concrete ceilings, doors and walls intended to withstand strikes from much heavier ordinance than anything in the Israeli arsenal. Leading North Korean expert on fortifications and underground construction Myong Lyu Do was confirmed to have travelled to Iran in 2005 to personally oversee these construction efforts. <a href="https://www.reuters.com/article/world/iran-nuclear-sites-may-be-beyond-reach-of-bunker-busters-idUSTRE80B0WM/" target="_blank">Serious questions</a> have been raised regarding the ability of the U.S. Air Force’s own <a href="https://militarywatchmagazine.com/article/dangerous-bomb-first-combat-gbu57" target="_blank">largest penetrative bomb</a>, the GBU-57, to destroy facilities at Fordow, with Western assessments having noted that multiple GBU-57s may need to be dropped to ‘layer’ attacks to reach such a deeply buried target. Should the United States deploy the bombs to support the Israeli-initiated war effort, however, the age of the B-2, the sole aircraft which can drop the GBU-57, and its resulting much more limited stealth capabilities relative to the modern F-35, has the potential to leave the small and high value fleet of just 18 aircraft exposed to taking losses.&nbsp;