http://en.wikipedia.org/wiki/First_Jewish-Roman_War
This set the wheels in motion.....2000 years later and it's still a crappy piece of dirt people fight over. It's not even good land.
Or if you really want to go back... http://en.wikipedia.org/wiki/Babylonian_captivity
The desire to return "home" has been deeply rooted in Jewish tradition. That, and the desire to have a Jewish tate in general. I'd generally consider the idea of establishing a country under a common ethnicity and cultural/religious tradition very backwards for the 20th century, but it's a little more understandable given how many people hated them for that ethnicity.
A lot of Christians also seemed to think it was the proper thing to do, particularly with Revelation talking about restoring Israel.. something of a self-fulfilling prophecy I guess.
One thing that the discussion so far regarding Israel vs Palestine/Arab world has left out (or at least I haven't seen it mentioned) is the amplified role the two played as proxies in the cold war.