"Without a doubt, the best strategy for collective defense of a society is to avoid armed conflict in the first place. Anarchist societies can do a far better job of avoiding conflict than states can. I will explain…
While certainly not the only factor in decisions regarding whether or not to go to war, the most important one is a cost/benefit analysis. It can generally be said that if a potential war will provide little utility to those who decide to embark on it, and that it will be costly, it most likely will not happen. This implies that states are likely to be highly aggressive, because the costs of wars are not borne by the politicians, but by tax-victims who are forced to fund them!
Additionally, the politicians’ cronies who profit from war (suppliers of bombs, bullets, guns, uniforms, tanks, jets, ships and other machines of destruction used in war - also known as the "military-industrial-complex") can certainly get significant benefits from it! Stateless societies, where those who choose to make war must fund it fully themselves, are far less likely to be aggressive. And luckily, what is needed for effective defense is far less expensive than what is required for military aggression.
A stateless society can drastically reduce the chance of conflict by making it costly to invade, and with as little benefit as possible to the invader. Without an already existing state in place, there will be no command center for the foreign aggressor to take over. Rather than simply taking over the capitol and using the already existing and “legitimized” state apparatus to extract taxes from the populace, the invader will need to win the war neighborhood by neighborhood. And if they succeed, they’ll need to create all the infrastructure needed to govern the hostile territory before being able to take from it!
In short, there would likely be very little to gain from attacking a stateless territory, at least financially. Contrast this with the possibility of invading a small state with a weak military. There is already an apparatus for control and administration in place, and likely only government defense institutions (rather than a decentralized network of private ones). Given that there are many governments today with weak militaries, they would be superior targets for invasion than a stateless region. And since these weaker states aren’t being constantly invaded in today’s world, that provides some evidence that large states may not be all that aggressive against a stateless society. You might want to double-check these facts, but from what I have found, there are 16 countries today with no military forces whatsoever, including noteworthy examples like Costa Rica and Liechtenstein, which hasn’t had a military since 1868.
"This is all well and good in terms of the economic motivations for war, but war is sometimes about more than that, isn’t it?"
Absolutely! There can be ideological or geopolitical motivations as well. In a stateless society, there would be no government to engage in significant disputes with foreign governments, and thus eliminate many of the potential causes for war. There may be individuals in the ungoverned area that are hostile to a particular state, but that foreign government will feel far less threatened by some hostile individuals than a hostile government. In addition, stateless societies would not be players in the power games and competition for domination in an area. There would be no standing army, and the society would not act as a single agent, so foreign governments will feel less threatened by the “power” of a stateless region. If still, a foreign army chose to invade, it would be clear to the subjects of the aggressing state that their government is in the wrong, which will decrease the aggressing state’s legitimacy in their (the subject's) eyes. With legitimacy being the source of the state’s power (the legitimacy of the State rests upon a perception of “consent of the governed”), going to war with a stateless region that has no standing military and is not perceived as a threat to the invading state would be a dangerous game for them to play.
"Nevertheless, it would be naive to argue that a stateless society will never be invaded."
This is true, but there are some easy ways that a stateless society could make it as costly as possible. For instance, protection agencies (being those who are most threatened by a potential foreign invasion) can put bounties on the heads of state officials to encourage insurrection and privateering (there is a great video about this which discusses what is known as the “Assassination market” and “Assassination Politics” you should check out, which was first conceived by a man by the name of Jim Bell). They can also assassinate those public officials, or create the credible threat that they could do so. Since protection agencies will be practiced at capturing/apprehending people, assassination or kidnap might be something they’re good at. Note: Government decision makers are far less likely to go to war if they know that it is their heads which are on the line. Protection agencies in a stateless region should ensure that the threat of retaliation is squarely on the political/military leaders, and not the soldiers and civilians of the foreign country. In fact, they can offer sanctuary or perhaps money to foreign soldiers in exchange for their desertion. If deserters bring some weapons with them, surely protection agencies would be willing to pay for those as well, and the local businesses, having no blind allegiances to any centralized government (“patriotism”) may even welcome the invaders, seeing them as potential customers!
"But couldn’t states, such as the US or Russia, just nuke the stateless regions?"
Technically yes, but remember that states can also nuke other states, and would have more reason to do so. Nuking a stateless region would offer no gain, would have long-lasting environmental impacts that could damage the aggressor state, and there would almost certainly be a loss of legitimacy internally in the eyes of the invading state’s subjects.
To sum up, there are many reasons to believe that a stateless society would have drastically lower needs for defense than a state would, and is unlikely to be attacked. In effect, the problem solves itself when the state apparatus is dissolved, but in the off chance that an invasion against a stateless society did occur, the market would already have a plurality of competing protection services (and other market entities) ready to respond in a variety of ways. Because it is in the best interests of those individual agencies (and their customers) to do so effectively and efficiently, they (the competing agencies) wouldn't even need a standing army or centralized power to do so, and the thought of having one would be silly when compared to all of the more effective (both in function and cost) defense strategies available in a free, adaptable and unfettered market.”
Note: I found this post in an online forum, but was unable to find the original author. I have since then (in this post) added to the original, and added the accompanying images. If you recognize this work, and know who the original author was, please let me know in the comments.
Thank you!