who's responsibility is it to ensure that something like the Moors invasion of the Iberian Peninsula would not happen?
That's one of the biggest problems that would have to be faced when putting an Ancap society into practice, and I don't have an answer for how it would be prevented in our world today, which is exactly why there are no Ancap enclaves. They would have to face not only getting invaded from every direction, but harsh sanctions from every country that doesn't want their authority challenged.
The first step to getting past this problem is to spread Ancap principles as much as democratic principles have been since the enlightenment. There are two ways of going about this: the first one is convincing people through discussion (and memes), and the second one is to establish a defacto-ancap society, and avoid the invasion/sanctions problem I mentioned earlier. The best we've come up with is literally colonizing the ocean, which we call seasteading, but technologically, that's far from being possible. When/if it is though, the hope is that international treaties will prevent existing nations from attempting to invade or tax the seasteaders, and a crackdown won't happen until the world really starts to notice that there are people living just fine without a government, just like how the American Revolution proved to the people of France/Europe that Democracy is just as workable as monarchy.
The first step to getting past this problem is to spread ... as much as democratic principles have been since the enlightenment.
I have to take a quick lol break. Democratic principles do not spread from the Western Governments, they install puppets in regions where they want resources, claim they were fighting oppressive or evil regimes, and proceed to absolutely fuck up the region. See Congo and Iran for prime examples of this. Cuba for where "democracy" failed.
Now, spreading democratic principles is in theory great. Some societies may end up working better in a democratic republic (like the US that is in absolute turmoil after a democratic election...), or a republic (rome/greece back in the day), or a monarchy (UK won the game of Risk). The West has fought several wars, overt and covert, in the name of Democracy, but mostly were for power and resources.
After so many fails at people being decent people...how could a good word of democratic principles spread?
What I mean is that most of the time when there's a civil war in some country, especially in pre-ww1 Europe, at least one of the sides wants to establish a democracy. This is because ever since it happened in America and France, the world has seen that a democratic government can be pulled off, and that made monarchy seem unnecessary, outdated, and tyrannical.
We want to do the same thing with Ancap principles. If somewhere, we can establish a society that functions just fine without a government, then people will see that government is unnecessary, outdated, and tyrannical. It's basically a faster, more effective way of convincing people it can work - because there's a real life example they can point to.
Hence why I still use a tiny credit union in a state I do not live in that only has a few branches and actually gives me several % interest on my checking account, so I put everything I can through them to help support them.
I completely agree with the whole "paper is worth nothing", banks are awful, government puts their greedy nubs into everything and wastes our generated currency by accumulating debt and giving away our nation's wealth, devaluation our currency, etc.
A true free market in theory can fix many issues, but in a true free market with a small government, who's responsibility is it to ensure that something like the Moors invasion of the Iberian Peninsula would not happen? Is that the government's fault for not being large enough to support a strong enough defensive? Should the local militias have the training and equipment necessary to defend against hordes of invaders? Should the free market always have a strong initiative to subsidize defense?
That's where it really breaks down for me. If our world was peaceful, AnCap would be great. But it isn't.