Original sentence: Up to 100,000 Palestinians, from the urban upper and middle classes in Haifa, Jaffa and Jerusalem, or Jewish-dominated areas, evacuated abroad or to Arab centres eastwards.While the Jewish population had received strict orders requiring them to hold their ground everywhere at all costs,  the Arab population was more affected by the general conditions of insecurity to which the country was exposed
Edited sentence: Please rethink it).Since the Jewish population was under strict orders obliging them to hold their zones at all costs, the situation of insecurity across the country affected the Arab population more visibly (this sentence does not make good sense (since implies that jewish self-defence caused Arab insecurity,and flight.Up to 100,000 Palestinians, chiefly those from the upper class, left the country to seek refuge abroad or in Samaria