When I saw the movie Exodus as a kid, the theme music had the line

"This land is mine, God gave this land to me" (majestic music in the background)

Even as a kid, I found this troublesome...

It is my understanding that just prior to the formation of the State of Israel, the area of Palestine was a British protectorate, and that when the British left, a UN resolution created the legal foundation for the formation of the new country. The UK aquired the land by conquest, after defeating the Turks, the previous governing authority. I may have the legalisms incorrect, but I believe that is essentially what happened. This new nation was settled by Jews from all over the world, but primarily from Europe, the survivors of the Holocaust. I also understand that there was already a small community of Jews living there amongst the Palestinian Arab majority.

The inhabitants of that region, were descended from people who had continuously occupied that land since the Romans forced the original Jewish inhabitants to leave en masse almost 2000 years earlier. This is not the first time that happened, the Babylonians carried off the Jewish people into slavery in ancient times to Mesopotamia, and after a captivity of centuries, authorized them to return, presumably displacing whoever was living there.

By the Jew's own traditions (although this has never been archaeologically verified, as far as I know) The land was originally occupied by Semitic peoples which the Jews expropriated by force, after their Exodus from Egypt.

The legal formalisms which created this state did not take into account the wishes of the people who were actually living there, which has led to trouble ever since. The prior claim of the Jews to that land, extending back to the Roman Empire, may have historical validity but I don't think anyone could use that today as a justification, particularly since by their own claim they were originally descended from Abraham, a stateless Mesopotamian nomad. It seems to me the Palestinians have a claim to the land.

Of course, every piece of real estate on the planet has been occupied by successive waves of peoples, the ownership usually settled by violence, so this is nothing new.

If the USA were invaded and conquered by a foreign power, and if after some centuries, that power chose to leave, it could legally (using the precedents cited above) return the land to the Indians who were historically the original owners. They would have the right to round up the non-Indian population and place them in reservations (also not without precedent). Think of the Native American peoples as the Jews,
and the European, Asian and African immigrants as the Palestinians and put yourself mentally in both their shoes.

It may be too late to do anything about it now, but the Palestinians do have a valid claim to that land. I'm not surprised they are in no mood to negotiate and not too happy about the folks who engineered this whole thing either. And although I tend to sympathize with the Jewish people, (because I have much more in common with them culturally) I'm not surprised how the Arabs feel about the way things have turned out.