The refugee problem is the most contentious issue in the historiography, as it frames the claim that Israel was born in ‘original sin.’ The classic Zionist narrative suggested the Arabs left mostly due to the calls of Arab leaders, and expected to return following an Arab victory. This claim began to be dismantled by Arab historians almost immediately, before being put to bed in the 80s by the Israeli ‘new historians.’
The Palestinian narrative has it that ‘population transfer’ (ethnic cleansing) was the Zionist plan all along, the war providing the long-awaited opportunity to secure a Jewish majority in Palestine. This narrative is supported by historians who point to the long history of thinking and discussion about ‘transfer’ in Zionist circles, certain operational plans executed during the war, and the argument that by 1948 there was no alternative plausible means by which a Jewish majority could be secured.
In response, a revised, more measured Zionist approach has emerged, arguing that while ‘transfer’ thinking was indeed a part of historical Zionist thinking about Palestine, its appeal was mostly contingent on circumstance (e.g. British support for the idea in the Peel Commission recommendations). They argue there was no clear pattern of expulsion of Arabs during the war - some commanders did it, others didn’t, sometimes it resulted from military/strategic necessity, sometimes it was done out of spite or revenge, etc. Finally, some imply that it was simply “us or them”, while others suggest that in the context of the first half of the twentieth century there was nothing particularly exceptional about what transpired.
700,000 refugees is at the lower end of estimates of numbers, normally I see around 750,00-800,000 cited by most historians.Many - perhaps a majority - fled without encountering a Jewish soldier. A small number of the more privileged (e.g. those who could afford to) left before things got really dirty, expecting to return soon. During the hostilities, many fled out of fear, due to rumors of massacres and other Jewish atrocities (Deir Yassin being the most infamous), or in advance of the arrival of Zionist forces. And there were some localized calls from Arab commanders to evacuate an area in anticipation of fighting. I don’t have the numbers to hand, but I think
Benny Morris concludes that something around 40% of those who left did so directly due to forced expulsion by Zionist forces.
I’ve already commented on the Israeli counter-claim regarding the flight of the Mizrachi Jews from the Arab states
here - it’s certainly a tragic episode, but I find its use in Israeli propaganda quite cynical, as it’s utilized in order to ‘balance’ the rights of the Palestinian refugees to justice, despite the fact that no matter what the reason for the Mizrachim’s flight was, the Palestinians were in no way responsible.
Finally, his claim that no refugees were offered citizenship by Arab states is wrong - Jordan offered citizenship to all those who came under Jordanian control in the West Bank in 1948.
*(edit): just checked and Morris describes 700,000 as a “fair estimation”