During the war, Britain had been a major sponsor of Arab nationalist thought and ideology, primarily as a weapon to use against the power of the Ottoman Empire. Although the Arab forces were promised a state that included much of the Arabian Peninsula and the Fertile Crescent the secret Sykes-Picot Agreement between Britain and France provided for the territorial division of much of that region between the two imperial powers. During the inter-war years and the British Mandate period, when Arab lands were under French and British control, Arab nationalism became an important anti-imperial opposition movement against European rule.