A lot of, if not most of, the current tension in the Middle East dates back to just after WWII, when someone decided it would be a good idea to stick all the people that no one wanted (but wouldn't come right out and say it) in the middle of a bunch of people who were ill-prepared to absorb them (and didn't particularly want them, either).
That pretty much paved the road to our current little slice of Middle Eastern hell.