Say a few billionaires got together and bought some land from a State, homesteaded some remote place, built an artificial island, whatever. It becomes very prosperous, but the US decides it is an Evil place, because it allows trade in drugs and weapons (or whatever other reasons the US can come up with), and decides to eradicate this libertarian paradise. How much would it cost to obtain sufficient nuclear/chemical/biological weapons and weapon delivery systems to deter the US from invading such a place? Assume the libertarian paradise is far away enough from the US that either ICBMs or nuclear submarines would be required to threaten the US mainland.
Expect nothing but random guesses. Jussayin.
Guesses are good enough for the mainstream media, why not here? The exact phrase: "a survey of economists" garners 191,000 results on Google, so presumably asking a group of economists their opinions on something has some legitimacy as a form of analysis.
Nuclear weaponry would probably be the best choice to stop the United States. Notice how the U.S. tends to treat nuclear powers nicer than non-nuclear powers?
As for price that is a good question. I doubt a government would sell the weapon, so it would have to be built. Getting the parts on the black market and the scientists to construct and maintain the nuclear weaponry could cost millions, but it may be cheaper. You don’t need the most advanced nuclear missile. A few ones from the 1970s or 1980s would be sufficient to blow up a couple regions/states. Expensive, but cheaper than maintaining a standing army.
Nukes may be too expensive, but I am confident there are chemical/biological substitutes that are nearly as effective and cheaper.
In Swordfish John Travolta says he can buy nuclear warheads for $40 million each...and even gets a discount if he buys half a dozen.
In modern times it's an extremely difficult calculation. For example nuclear weapons are an excellent deterrent but their efficiency may be waning: see how the US keeps on threatening and bullying Pakistan, a nuclear armed State.
Estimating the costs of a nuclear program alone is tricky. Israel probably got their first nuclear weapons (presumed by analysts to be 20kt gun-type devices) relatively on the cheap. Of course these were crude, heavy and relatively ineffective devices cobbled together in a hurry a few days before the Six Days War. Delivering them would have been a headache if not a downright nightmare. Yet in just six years Israel was able to field tactical warheads every bit as advanced as those available to the US and the Soviet Union: following the meeting of Golda Meir's "kitchen cabinet" during the Yom Kippur war both the Phantom fighter-bombers based at Tel Nof and the Jericho missile units at Hirbat Zachariah were on full alert and ready to strike by the next morning. Yet how Israel managed to advance so much in so little time and, apparently, with scant funding remains a mystery. While how they obtained raw materials has pretty much been made clear, where and how they got the tech is a mystery to this day. In the following twelve years Israel managed to catch up completely with both the US and the USSR: data and pictures provided by Mordechai Vanunu had one American analyst saying "They can do anything we or the Soviets can do". How they did this is, of course, open to speculation.
Estimating the costs of a delivery system is another problem. Israel got her first nuclear delivery system "out of the box" from France in form of the Mirage III fighter. This capabilities were substantially upgraded when A4 Skyhawk and F4E Phantom II were delivered by the US in 1969 with their nuclear capabilities still intact ( a fact recently surfaced and denied for years by US authorities). The Jericho I short-range missile was built using tech supplied by France before the arms embargo. Yet both the Jericho II and the Jericho III are a huge step forward: the Jericho III can reach North America and employs tech so advanced (in form of ABM-avoidance) it's well ahead of anything the Russians and the Americans are fielding at the moment. Again how much did it cost? Whence came the tech?
There's also another thing to consider: you cannot just go around and openly threaten nuclear annhilation, even to a big bully like the US. Truth to be told you cannot even openly declare a Samson Option, which would be strictly defensive in nature. Nuclear weapons work in a subtle way and, as again Israel demonstrated, can also be used as a bargaining chip. During the First Gulf War Israel got huge US aids just by making veiled threats about replying to a possible Iraqi chemical strike "in nature".
There also other options to consider. One of the reasons Iran still hasn't been attacked is the unfathomable cost of a military action against it. Yes, bombers and cruise missiles can strike from the sky, but to bend a country to your will you need "boots on the ground". The costs of occupying Iraq and Afghanistan have been staggering, and the local insurgents had access to limited weaponry and limited training. What would have happened had they been better armed and trained? What if they had access to, say, vast quantities of advanced MANPADS and AT weapons? What if they had been trained in "terror tactics" aimed at sapping the enemy's morale? What if they had access to the drone counter-measures Russia has developed? Iran can easily do this and make the occupations costs absolutely unbearable for realtively little cost to herself.
Hope I gave you something to chew on.
Interesting considerations. I think the one big difference between a libertarian/anarchist nonstate and the likes of Israel, Iran, North Korea and such is that the libertarian one would be much smaller, as it would probably have to be either built from scratch (such as seasteading) or purchased from an existing State at exorbitant rates. This would rule out guerilla warfare, terror tactics, etc., as even a large conventional bomb or two might be enough to entirely destroy the libertarian area. Hence why a nuclear submarine or two might be a good idea, so that a preemptive strike against the libertarian area wouldn't remove the threat of retaliation, which would make any such preemptive strikes against it less likely.
SSBN (nuclear-powered submarines armed with long range nuclear-tipped missiles) are a powerful form of deterrent but their strategic role is "second strike capability", meaning the possibility of launching a retaliatory strike against a foreign power even if this wiped out land and air based nuclear capabilities with a pre-emptive strike. There's a reason the US and Royal Navies kept a close watch on Soviet SSBN's during the Cold War.
I haven't quoted Israel at random. Israel is a small country with limited defense depth capabilities. It means an invader has just a few lines of defense to crack to get to the heart of the country. It also has small manpower relatively to her neighbors. Israel recently acquired a second strike capability in form of modified German Type 212 submarines. From a technical point of view this was not the best choice: both the Soviets and the Chinese experimented with conventional-powered submarine missile carriers (SSG) and they found the solution lacking. SSG lack the endurance to stay on months long patrols (necessitating just crew changes and replenishing supplies) and are limited in size, hence carrying just a handful of missiles. However SSBN are rabidly expensive and owning them means entrying in the "big boys' club". China only has four and, judging by what we know, they are almost straight copies of Russian Delta IV/Delfin SSBN. Here costs are pretty well known: the US Navy Ohio SSBN cost two billion dollars apiece to build back in the days (plus missiles, crew training etc); the proposed replacement (SSBN-X) should be twice that money but recent military acquisition programs all over the world have run into such massive cost overruns and delays that should be considered just a vague assessment.
So the answer seems to be 'keep a low profile'.
Excellent global trade relations would probably be a good deterrent as well. Look at neutral countries and emulate their success.
Don't we already have such an answer?
Aren't there existing privately owned states? They may not fit the libertarian ideal, but I think the UAE might qualify as such a realm.
I think that fact that you provide the ability for rich people to come and get cheaper high-end products than are available elsewhere carries within itself it's own protection. It is the rich/powerful (kind of the same thing) within any society which end up ultimately making the decisions about where and how the political might of the nation state is wielded.
My guess is that unless the new state engages in some type of non-free trading intervention that there would be no external pressure to aggress against a privately owned state.
The other mechanism, not military might, that such a social institution might use is PR. 90% or more of political "combat" is fought in the "hearts and minds". As it must be in democratic societies.