Mandatory Palestine, existing from 1920 to 1948, was a territory under British administration as per the League of Nations' mandate following World War I. This period followed the Arab revolt against Ottoman rule and the British military campaign that ousted the Ottomans from the Levant.^[165] The post-war geopolitical landscape was shaped by conflicting promises and agreements: the McMahon–Hussein Correspondence, which implied Arab independence in exchange for revolting against the Ottomans, and the Sykes–Picot Agreement between the UK and France, which divided the region, seen by Arabs as a betrayal.

Further complicating matters was the Balfour Declaration of 1917, where Britain expressed support for a Jewish "national home" in Palestine, conflicting with earlier promises made to Arab leaders. Following the war, the British and French established a joint administration over the former Ottoman territories, with the British later gaining legitimacy for their control over Palestine through a League of Nations mandate in 1922. The mandate aimed to prepare the region for eventual independence.^[166]

The mandate period was marked by significant Jewish immigration and the emergence of nationalist movements among both Jewish and Arab communities. During the British Mandate, the Yishuv, or Jewish community in Palestine, significantly grew, increasing from one-sixth to nearly one-third of the total population. Official records indicate that between 1920 and 1945, 367,845 Jews and 33,304 non-Jews immigrated legally to the region.^[167] Additionally, it's estimated that another 50–60,000 Jews and a small number of Arabs (mostly seasonal) immigrated illegally during this period.^[168] For the Jewish community, immigration was the primary driver of population growth, whereas the non-Jewish (mostly Arab) population growth was largely due to natural increase.^[169] The majority of Jewish immigrants came from Germany and Czechoslovakia in 1939, and from Romania and Poland during 1940–1944, along with 3,530 immigrants from Yemen in the same period.^[170]

Initially, Jewish immigration faced minimal opposition from Palestinian Arabs. However, the situation changed as anti-Semitism intensified in Europe in the late 19th and early 20th centuries, leading to a marked increase in Jewish immigration to Palestine, predominantly from Europe. This influx, coupled with the rise of Arab nationalism and growing anti-Jewish sentiments, led to increasing Arab resentment towards the growing Jewish population. In response, the British government implemented quotas on Jewish immigration, a policy that proved controversial and was met with dissatisfaction from both Arabs and Jews, each for different reasons. Arabs were concerned about the demographic and political impact of Jewish immigration, while Jews sought refuge from European persecution and the realization of Zionist aspirations.

Tensions between these groups escalated, leading to the Arab revolt in Palestine from 1936 to 1939 and the Jewish insurgency from 1944 to 1948. In 1947, the United Nations proposed a Partition Plan to divide Palestine into separate Jewish and Arab states, but this plan was met with conflict.

The ensuing 1948 Palestine war dramatically reshaped the region. It concluded with the division of Mandatory Palestine among newly formed Israel, the Hashemite Kingdom of Jordan (which annexed the West Bank), and the Kingdom of Egypt (which controlled the Gaza Strip in the form of the "All-Palestine Protectorate"). This period laid the groundwork for the complex and ongoing Israeli-Palestinian conflict.