[nirimda]

Not just the existing nation states who want to reclaim the land, but also anyone else. Maybe Russia will recognise you for free, but no one else will. They will want something out of it. And they will have to believe it is cheaper to get it by recognising you than by defeating you.

For instance, going back to the "about the size of Singapore" example, OP might try to find a nice perch next to some critical strait, and sink any vessel that passes through which is registered in a country that doesn't recognise them. But if OP gets too good at this, then the US Navy will be upset and start shooting their weaponry at OP. If OP manages to sink a few of USN's vessels, it's possible USN will say "well we will stop shooting you if you let through our vessels", but I wouldn't hold my breath.

It's probably just cheaper and easier to marry into a royal family from some small country that whose royals still have a political power, like Brunei or Liechtenstein, then secretly start a secret murdering spree until your newborn is the only royal left and they offer to make you regent, then launch a self-coup against your own six month old.

[max_]

Well, that got very dark.

I am not that kind of vibe. I was wondering if you could just legitimately purchase some land from a country will to sell, then establish sovereignty?