The causes are also a subject of fundamental disagreement among historians. Factors involved in the exodus include Jewish military advances, destruction of Arab villages, psychological warfare, fears of another massacre by Zionist militias after the Deir Yassin massacre, which caused many to leave out of panic, direct expulsion orders by Israeli authorities, the voluntary self-removal of the wealthier classes, collapse in Palestinian leadership and Arab evacuation orders, and an unwillingness to live under Jewish control.