There are plenty of analysts who deal with the logistics of nuclear weapons and their interdiction in the abstract, and a very few who have dealt with the matter as an existential issue. Apart from the Israelis, for whom Iranian nuclear capability represents an existential threat, the list is short. The German defense expert Hans Rühle headed the Policy Planning Staff of Germany’s Defense Ministry during the 1980s, when the U.S. installed the medium-range Pershing missiles in Germany and undercut Russia’s military advantage in the European theater. A nuclear exchange with Russia remained a live possibility in those days; after the Cuban Missile Crisis, the high water mark for strategic risk during the Cold War came in 1983, when then-Soviet premier Andropov declared a nuclear alert, ostensibly in response to NATO’s “Able Archer” exercise, but really as an attempt to panic the Germans.
Hans Rühle was one of the toughest and most perspicacious analysts in those heady days. Today he evaluates Israel’s capacity to knock out Iran’s nuclear program in an essay in the German conservative daily Die Welt. It is worth reading (for non-German speakers, there’s Google Translate).
Rühle is highly confident that Israel could knock out Iran’s nuclear program for a decade or more with about 25 of its 87 F-15 fighter-bombers and a smaller number of its F-16s. Each of the F-15s would carry two of the GBU-28 bunker busters, with the F-16s armed with smaller bombs. Rühle writes
There are 25 to 30 installations in Iran which are exclusively or predominately dedicated to the nuclear program. Six of them are targets of the first rank: the uranium enrichment facility at Natanz, the conversion works in Isfahan, the heavy water reactor in Arak, the weapons and munitions production facility in Parchin, the uranium enrichment facility in Fordow, and the Bushehr light water reactor.
The location, nature, and defenses as well as (with some limitations) the type of installed anti-aircraft systems are extensively known.
The information about Natanz are solid. The project has been under satellite surveillance from the beginning and watched by Israeli “tourists.” At the moment there are a good 10,000 centrifuges installed, of which 6,500 are producing. Israel’s strongest “bunker buster” is the GBU-28 (weight 2.3 tons), which demonstrably can break through seven meters of reinforced concrete and 30 meters of earth. It would suffice to break through the roof at Natanz. In case of doubt, two GBU-28s could be used in sequence; the second bomb would deepen the first bomb’s crater and realize the required success.
Available guidance systems, the German expert adds, are quite adequate to guide the bunker-busters to their goal in this fashion. Only a few bombs, he adds, would be required to destroy all the centrifuges; spinning at 1,500 revolutions per second, these instruments turn into grenades when destabilized. With a few hits, all the centrifuges would be destroyed beyond repair.
Fordow, by contrast, is a harder target, with about 3,000 centrifuges under 70 meters of rock. Even the U.S., Rühle says, does not have bunker-busters that can penetrate that far. The deployment of special forces is a more likely option. The other targets (the light- and heavy-water reactors) are far softer, and F-16s with lighter munitions would suffice.
Parchin is the “bottleneck” through which all nuclear materials must pass, the weapons production facility where warheads are designed and tested. “How many bombs would be required to destroy Parchin,” Rühle says, “is a matter of speculation.”
Most importantly, Rühle believes that it would take Iran a decade to restore its capabilities — with the exception of Isfahan — unless special forces could inflict more damage from the ground than was possible from the air. There are risks, of course: the Russians might have secretly given Iran more advanced surface-to-air missiles; refueling might be interdicted along a route that overflies potentially hostile countries; and Iran’s proxies (Syria, Hizbollah, Hamas) might retaliate. Nonetheless, he concludes that Israel could lastingly disrupt Iran’s nuclear program.