At the time, the Jews constituted only a third of the population. The hundreds of Arab villages throughout the country dominated the main arteries that were crucial to our survival. We suffered heavy casualties in our efforts to open them, especially the road to Jerusalem. We honestly felt that we were "the few against the many".
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Our side was preparing for the massive attack of the Arab armies and we could not possibly leave a large hostile population at our rear. This military necessity was, of course, intertwined with the more or less conscious desire to create a homogeneous Jewish territory. [... A]ccording to the UN resolution, the "Jewish state" was to include more than half of Palestine (as it existed in 1947 under the British Mandate). In this territory, more than 40% of the population was Arab.
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In the second half of the war, after the advance of the Arab armies was halted, a deliberate policy of expelling the Arabs became a war aim on its own.