Since the late 1970s, most scholarship on the origins of the Zionist–Palestinian conflict has emphasised the actions and agency of the Palestinian Arabs and Zionists, with a focus on the period before 1914. It is argued in this article, however, that the expectation of and commitment to political independence on both sides, a defining feature of the conflict, did not emerge until 1918, and that the actions of the British government in Palestine during the final year of the First World War drove this fundamental shift. Following Britain's occupation of southern Palestine in December 1917, the British administration undertook an extensive propaganda operation in the country to advertise their backing for Arab nationalism and Zionism. This campaign was part of the British government's wider endeavour to mobilise support for the Allied war effort and British imperial expansion in the Middle East in the new age of nationality. It led, the article contends, to a war for national sovereignty over Palestine between two statist nationalist movements. Rather than emphasise British colonial agency at the expense of that of the Palestinian Arabs and Zionists, the article argues that this development derived from a complex interaction between the three parties within the context of radical changes in international politics.