A lot of military infrastructure is becoming electronic in nature. If we wait a few years and then fill up seasteads with computer security experts and hackers, well, that'll be an army all on it's own. Remember the little country of Estonia and how Russia recently defeated it in a recent internet war, devastating Estonia's infrastructure? Have internet, will travel.

Seasteads, like many small independent communities, could easily fund themselves by serving as independent Internet Servers and engaging in ebusiness, then using the revenue to buy more satellite bandwidth, computers, and Seastead property... ad infinitum.

The best defence a seastead can have against nation-states tagging it "threat", is to develop economical ties with the people and corporations inhabiting those nation-states. Not only does it create wealth for sustaining the growth of seasteads, but it also makes a lot of rather important or influent people onshore more or less dependent on your continued success at sea.

However, such ties may also render seasteads vulnerable to economic sanctions, which would give tyrants everywhere a foothold for imposing unwanted regulations. Have a look, for example, at what happened to tax havens in 2001-2002, following 9/11. The main rulers of the world WILL come to an agreement together to abuse seasteaders if they ever get the opportunity. I would advocate aiming for self-sustainance and smuggling against such a threat, but they both have an impact of economic efficiency, so that would hamper growth.

Bulk size, in both land acreage and population, could also help defend against this threat, but it's a very long shot. The same goes for that "Teleforce" thing: it's hardly even hypothetical.

Let's also remember one point of dynamic geography, which is that onshore foreigners will (should !) be tempted to migrate in. That could make "cultural ties" possible, but could also be frowned upon by governments not so eager to have their taxpayers leak away.

• Live video broadcasting from the seastead (webcams essentially) could perhaps make a potential invader think twice. Videos of country X´s special forces guys committing an act of aggression on the peace-loving seastead community all over the internet could have some (and by "some" I do not mean "complete") deterrent effect. And it´s a completely benign , or "non-aggressive", for lack of a better word, form of "defence".
• While I do not doubt Nikola Teslas genius, this "Teleforce" thing seems somewhat untested as far as I know. I´d personally go with regular small arms as my main defense, and perhaps some heavy machineguns and anti-tank (anti-boat?) weapons thrown in for good measure. If some nation-state intends to actually obliterate a seastead there will be no reasonable way of defense, so I´d rather concentrate on defending againts invasion and infiltration. Some CIWS cannons and Stinger missiles could be useful for defense against missiles and aircraft but theyre probably hard to come by as well as giving said nation states a perfect excuse to label us terrorists.
• edit: Should anyone actually prove that the Tesla weapon or something similar really works I´m all for it.

 I don't understand why the threat of Piracy is so blithely dismissed.  Violent crime is the only real physical threat to a technology advanced society of silicon valley millionaires.  I think it is the word "pirate" that makes people so dismissive - like we are thinking of Johnny Depp with an eye-patch.  Modern pirates are simply the same criminals as we would encounter on land in any remote place.  Armed men with access to military grade weapons (often they are part of military or paramilitary forces) led by smart, motivated professional criminals who know exactly the value of their target and how to capitalise on it.   Rape, pillage and murder are just unpleasant side effects in their eyes to the pursuit of material gain.  Kidnapping is an obvious target as well as removal of computer and communication equipment, fuel, water/air craft and any other technology that is otherwise hard for these types of groups to obtain.  

"Maritime piracy is back on the foreign policy radar screen. Reported attacks against commercial ships have tripled over the past decade, increasing last year alone by 40 percent.¹ Nearly two-thirds of thew attacks in 1999 occurred in Asia, with 113 of the 285 reported cases taking place in Indonesia's waters and ports. The risk of attack is increasing with 90 percent of the world's trade moving via ship and 45 percent of all shipping moving through the pirate-infested waters of Asia. Clearly, piracy is becoming an increasing threat to global trade." http://www.heritage.org/Research/AsiaandthePacific/BG1379.cfm

Only a well equipped and well organised para-military force could be relied upon to negate this threat, and the existence of such a force introduces some very old world problems around the morality of mercenaries, the relationship of military service to social power, and the costs of a standing navy, into this idealistic societal concept.

The threat of governments trying to "take down" this off-shore threat is laughable.  It is very unlikely (Why do we assume the Seastead community is going to be seen as a threat?  What are we planning on doing? An why bother with a military assault when you can simply blockade supplies, close bank accounts and stop any flights to/from those communities)   and if it occurred it is completely unstoppable by force, so it should be ignored.  If anyone serious, any member of the G8 for example, had any reasonable proof of "terrorists" or "criminals" being supported or protected by a Seastead community they wouldn't think twice about sending a couple of gunboats out to pick up all the inhabitants and take them off to jail - where many would probably be repatriated to whichever home country claimed them.  Any amount of real military hardware (stinger missiles et al) would only increase the use of force, and the idea of a Tesla weapon is so ridiculous I can't believe someone even brought it up.  At the risk of giving this idiocy undue notice, if such a "death ray" existed, that existence itself would be more than enough excuse for any major power to reduce the Seastead to matchwood.

The best suggestion for protection from states is the use of positive PR, including constant web feeds.  Of course getting a G8 member to recognize your sovereignty is the real key to security.

As long as people don't renounce their passports, or offer too much of a FUCK YOU to the nation state governments, in any real bother people's own governments will send commandos to come and rescue them, as happened recently to those french folks who's yacht was attacked by pirates.

That's the fundamental backup and probably always will be. And that's a good thing.

Realistically the most any commuity is going to need is a few small arms for a local milita to protect themselves against criminal elements, larger commuities might want some mounted light machine guns or at most some surplus 20mm autocannons.

If you need CIWS, stingers etc your trying to fight a military force so your screwed anyway.

Well aside from political considerations and avoiding the appearance of aggression, here's a couple points on weapons:

• Any half-decent mechanic with a shop of tools can build a shortrange cruise missile, or crude torpedoes. Off the shelf electronic components from hobby shops or on the Internet far surpass anything available for remote guidance up until the Gulf War.
• Stingers may be harder to come by, and more expensive, but there's also a lot of SA-7 Grails around the world.
• Full-automatic AK and M16 variants are easy to come by around the world (I personally know this for a fact- you can't sell a fully auto AK-47 in Iraq for more than maybe $100), and as long as you don't bring it past the custom demarcation point in port, nobody even cares. Crew-served weapons (.50 caliber machine guns etc.) are probably just as easy, if costing a bit more. Grenade launchers- all easy. They cost money, but not so much that a few people together could not affford a decent number and variety of weapons.
• You have no- zero- zip- not a snowflake in hell's chance against a professional navy or air force. You can't run, and you can't hide.

Main problem seems to me underwater defence. If they just sink you with torpedos, what good will those cameras do for example. It might be even be hard to prove somebody atacked you. Let alone who did it.

so basically what i am getting is that the best way for a seastead to survive would be to have strong economic ties with one of the global super powers so that, while yes the amount of freedom will be decreased, it will not be decreasd by much and it will also have an insurance policiy against any foreign intervention in the seasteads affairs other than its main economic partner

• thanks for the posts though, they were very helpful

• Underwater cameras. Even a camera on top looking at the sea might have a chance of seeing the torpedo. In any case a bunch of webcams is hardly a major drain of resources and they have other benefits like good PR so there is no point in not having them.
• A seastead can conceivably be equipped with sonar, depth charges and torpedoes of its own, to fight underwater threats.