Writing this on my iPhone, so it’s hard for me to provide a link. But wouldn’t it be possible to do something like land a few hundred helicopters, and just take over and destroy the facility while defending against whatever forces they can throw at it in that period of time. Or is this completely unrealistic.
Of course it’s possible to destroy this site.
It’s only a matter of whether it’s worth doing.
A whole lot of people will be killed, and lots of equipment destroyed.
On my first impression it seems nearly impossible. Helicopters are vulnerable things, and while there have been some recent examples of stealth helicopters I doubt anyone could sneak in 100. Many, if not most, would be shot down before landing. Then, the ground forces have to assault the facility, which is heavily fortified. A fortification capable of surviving a nuclear blast is probably impervious to any weapons that can be carried in a helicopter. Finally, even if such an assault worked (against all odds), the forces won’t have any means of escape. After such a battle, there’s no way any of the helicopters could make it out of the country, and there would loads of regular army units on the way to retake the facility.
Impossible to bomb is kind of how I like my nuclear bunkers, etc. Doesn’t everyone?
You could always… bomb a path for the helicopters, couldn’t you? 
Ok, so let’s say I build my long-planned secret lair in a bunker that is 1,000 feet below ground. There is no way in hell that any weapon could conceivably go through so much dirt to actually penetrate the bunker and deliver the warhead.
But I do not plan on being entombed in my bunker. I need at least one tunnel for my henchmen to exit to go get lattes, smokes and milk at the 7-11, not to mention some way to get air, water, and other necessities in. If those passages are destroyed, how much difference does it make if the physical bunker itself is immune from direct attack, whether from the air or by ground forces?
Not to mention a large, slow moving ventilation fan for your enemies to get by.
I’ve wondered the same thing along a different tact. How hard would it be to blow up using repeated conventional explosives? If we just keep dropping the MOAB’s, or something similar, wouldn’t we eventually get there? First bomb makes a hole, second bomb makes a bigger hole, etc.
I know this wouldn’t be realistic as it’s probably take quite a few bombs to get there and Iran isn’t exactly going to sit back and let us keep flying sorties, but it’s certainly doable, right?
Nothing is immune to attack from ground forces, if one human can get there, more can follow.
The post by lazybratsche is patently absurd. There is no way that Iran would successfully shoot down “many if not most” of U.S. helicopters flying in Iranian air space.
That’s really irrelevant though, we’d never send in ground forces unless we were already at full scale conflict with Iran, in which case we’d send in a large strike force after massive bombings destroyed Iran’s air defense grid. Experience in various aerial campaigns of the late 20th century suggests we would probably have Iran’s air defense systems mostly ineffective in a few days. After that unconventional forces can take out a helicopter with RPGs and things of that nature, but that’s a poor deterrent against a strike force, RPGs are better for picking off helicopters slowly over time, not for defending against a large scale helicopter-transported strike force.
If we get into a shooting war with Iran (not invade, but just be at full scale war in the Gulf with naval/air forces fighting Iran’s naval/air forces) I could see us potentially sending a strike force to facilities like these. Once you have Iran’s air defense system neutralized a facility like this wouldn’t really be impossible to take out. You just heavily bomb the area to soften up any of their ground forces and then blow up the entrances and pour a bunch of nasty chemicals into the bunker and make it uninhabitable, then collapse all the entrances and exits under the mountain itself and while the interior of the bunker won’t be destroyed it certainly won’t be realistically usable any longer.
https://download.nap.edu/catalog.php?record_id=11282
Relevant reading.
Think of dropping a bomb down a well. Most of the explosion in the dust are contained in the well. So as you get deeper, less and less of the dirt is being blown out of the hole. If you have to go 100 feet deep, well, that’s a lot of dirt you need to blow away. I doubt it’s practical.
Good cite. Thanks.
An operation of the sort suggested in the OP is not a surgical strike, whether or works or not; it’s an invasion and a rather outrageous act of war, and Iran would be legally and morally justified in taking any military action it deemed necessary to defend itself. They’d also be bound to do so just by virtue of having to protect their strategic assets.
In other words, even if it worked, it’d be the least of your immediate worries, since you just started a full scale war.
How so? Helicopters are slow, noisy, and vulnerable. Alone against Iran’s air defense system, they wouldn’t stand a chance. Hell, they wouldn’t even be able to evade (much less fight) old Soviet fighters. Or even vintage flak emplacements. And since everyone talks about a possible air strike on Iran’s nuclear facilities, I’m guessing there are considerable air defenses in and around the area.
Sure, the US has demonstrated the ability to sneak a couple stealth helicopters to an undefended site. But I doubt there are “hundreds” of such helicopters (though anyone who knows otherwise certainly wouldn’t post here!) And I doubt that such a massive number of stealthy helicopters could remain undetected.
Now, the rest of your post I pretty much agree with. The Iranian air force and air defense wouldn’t last long in large-scale bombing campaign, much like the Iraqis in '91. After the air defenses are destroyed, the US could launch an airborne attack, but perhaps it would be easier to bomb and interdict the facility as much as possible.
Purely hypothetically, just as was the case with bad guys hiding in caves in Afghanistan, you don’t need to collapse a cave, you just need to seal in the inhabitants like in Poe’s A Cask of Amontillado.
A quick-hardening cement cap in the right place (or a few places) would do a fine job. I don’t know whether one could be “dropped” into place (I can’t rule it out-- considerable creativity has been shown by ordnance designers in the past) or whether engineers would have to be landed and protected while creating one. Theoretically the force could then exit the area and slather the capped entrance(s) with “area denial” cluster munitions (to inhibit rescuers from drilling through the cap in time).\
I don’t advocate bombing Iran, I am purely discussing a theoretical approach to any hardened underground facility.
Luckily, all tunnels come with caps in place, the overburden. Ideally you would collapse the entrances and ventilation with munitions. The problem with that would be finding them.
Well, we’d have to assume the choppers would be escorted, and the Iranian AF can’t touch a modern US Fighter. On air battles between the F-18 & co vs the Iranian F-5 clone they currently fly- the only limitation is how many Saeqeh the F-18s can shoot down before the F-18’s run out of ordnance.
During the second world war, the british engineer Barnes Wallis realised that bombs are way more effective if they are surrounded by a medium that transmits shockwaves (i.e. not air). So he designed a bomb that exploded against a concrete dam while damped by the water in the dam that would transmit a shockwave through the dam and break the concrete. Getting against the dam over torpedo nets was a completely different problem. And so the Dambusters raid (Operation Chastise) destroyed two dams on the Ruhr in the German industrial heartland.
The “success” (there is dispute as to the longterm disruption to German industry, but the morale boost for the Allies was high) of Chastise allowed Wallis to begin work on his other bomb project - deep penetrating bombs that transmitted the explosive shockwave through ground and rock to damage and undermine large structures. Starting with the 5-ton Tallboy and moving to the 10-ton Grand Slam, these weapons were used to disrupt German facilities and transport infrastructure.
Even if they did not directly hit fortified concrete targets, a near miss could disrupt the foundations of V2 launch sites, completely mis-align the V3 long-range cannon facilities, and collapse bridge spans into the ground. Some may have penetrated the reinforced concrete of E-boat pens. They were just as destructive in water, with Tallboys damaging the Tirpitz so it never posed a threat to allied shipping.
The US has a deep-penetrating bunker buster (bigger than the Grand Slam). Whether or not they are sufficient to cause significant structural damage to a bunker as deep as the Iranian facilities may be uncertain, but it will probably damage and disrupt delicate engineering equipment (centrifuges and precision machinery). It will most likely damage the structural integrity of the surrounding rock, and damage access shafts. They might not be able to completely destry the facility, but I suspect that the damage of a few deep penetrating bunker busters would make the facility functionally useless for many years.
I think therre needs too, to be a distinction between high-flying jets that need a fairly hefty missile to take them out, vs helicopters at almost ground level that are vulnerable to shoulder-fired missiles. And also consider just how many troops you can send in on helicopters versus how many the Iranians can truck in, or have already located there.
The question that are important - can the US ordnance actually reach the facility at the depth it is? And do you know how many alternate exits exist?
There’s a law of diminishing returns in attempting to dig with bombs, one blast at a time. Eventually, you start collapsing the walls of the hole. I’m not sure what the dynamics of blasts are, but I would imagine tricks like zig-zag tunnels help mitigate blast fronts. Also, giant heavy doors.
Then consider whether the assorted US bases or ships in the region can effectively guard against missiles that apparenly Israel cannot? And whether they want to escalate to the point where Iran blocks oil shipments at Hormuz or attack oil facilities in the gulf in retaliation? Right now Iran is avoiding anything except attacking Israel, which started this. When they are facing massive annihilation anyway, there is nothing to limit their retaliation.
Does anyone remember the last time we sent helicopters deep into Iranian territory?