You make a good point, while the right of discovery can be used in some more remote areas of the world, for the most part, the right of conquest prevails as the basis for claiming land, that most countries occupy today.

I did not say it was okay for Russia to conquer Ukraine. I am merely outlining the historical basis for claiming rights over land.

Using your example of Ukraine, what I am saying is that under the theory of the "Right of Conquest" that at some point in the future if Russia successfully conquers Ukraine, it will move from being "occupiers" to having a right to the land.

You do raise one of the issues related to the right of conquest and that is how long does it take for a nation to establish its claim over land under the right of conquest.

For example, parts of Germany are now parts of Poland, France and Czech... do you believe Germany has a right to those lands or having lost them in prior wars, do they now belong to Poland, France and Czech. Finland and Mongolia have the same issues with Russia and China, respectively. Mexico has similar issues with the US over areas on our border. Tibet is another example.

In an attempt to mitigate "territorial wars" the world began looking at a different model. The right of "self-determination". Let the people residing in a country decide. This is a very western concept predicated on the idea of democracy and that governments exist to serve the people (rather than people exist to serve the government). That idea did not get very far in a world where democracies are not as prevalent as once hoped.

So, that leads back to the "right of conquest" with some strings attached.

Those strings take the form of international recognition and peace treaties. Once enough nations acknowledge the conquest as a "fait accompli", the land belongs to conquerors. That is how the world works today.

Looking at Israel it was recognized by the UN as a full member in 1949 by 165 nations. Arguably, as far as those 165 nations are concerned, Israel has a right to the land it had at the time its borders were recognized by most of the world.

Since then, Israel has acquired some additional territory through wars and returned some (like Sinai to Egypt). With respect to the two-state solution, Israel is proposing to give Palestinians the remaining territory it acquired in subsequent wars plus some of the territory recognized as part of Israel for them to have as their own state in exchange for Palestinians acknowledging Israel's borders and right to exist.

The Palestinians to this point have been unwilling to do that. Arguably, if the Palestinians were able to conquer territory belong to Israel based on the UN recognition of Israel's land, they would be "occupiers" until they held the land long enough to gain international recognition of their right to the land.

Bottom line, the right of conquest is still the primary driver, but since WW2 the world has inserted "recognition" of such conquest (by the UN or World Court) as an added requirement to extinguish competing claims.