The origins of the protracted conflict between the Arab world, especially the Palestinians, and Israel, dating to the emergence of Islam in the seventh century of the Common Era, are explored in terms of four levels of conflict. The conflict began with a Clash of Belief Systems, Islam versus Judaism. It escalated to Competing National Goals of Arab and Jewish nationalism. It escalated further in the form of Intercommunal Rivalry between the Arab and Jewish communities in Palestine, from the beginning of the Return of the Jews to their Ancesteral Homeland in the 1880s. Moreover, this conflict was intensified by Discordant British Pledges to the Arabs and the Zionist movement during World War I (1915 and 1917, respectively), which became a persistent source of Arab-Jewish conflict throughout the League of Nations Mandate in Palestine (1923–48).