According to Palestinians, they were expelled from Israel by the Jewish armies in 1948. A large amount of existing documentation, and many testimonies from Arab leaders and historians prove that, actually, they fled the zone of conflict because of Arab propaganda, and spreading rumors of (fake) massacres--one of which was Deir Yassin which became a legend. Decades later there would be Jenin and Gaza, and on and on. In typical pallywood format the Arab PR machine works hard to change history. It is so much easier to believe a lie than search for the truth.