During the First World War, the Ottomans undertook a pan-Islamism propaganda campaign through the newspaper al-Sharq (published by Djemal Pasha in Damascus) to motivate its Arab subjects to support the Ottoman struggle against the Entente powers. To this end, many articles and news items appeared in al-Sharq to inspire Muslim unity around the figure of the caliph. Unity was presented as a crucial part of saving Muslims; disasters were predicted should the Ottoman Empire fall to the 'infidels'. Sharif Husayn and his followers were explicitly or implicitly accused of splitting the umma and rendering the Hijaz and the remainder of independent Muslim territories vulnerable to British and other European imperialists. In 1916, Sharif Husayn launched a revolt in Mecca against the Ottoman Caliph and established a periodical, al-Qibla, to target the same audience. In al-Qibla, Husayn presented the Committee of Union and Progress as amoral and irreligious usurpers of the caliph's authority, and therefore undeserving of allegiance. In this article I analyse the discourse of the two competing sides by examining their propaganda on issues such as loyalty to the caliph, the unity of the Muslims and the formation of alliances with the Great Powers. I argue that Islam shaped the propaganda battle between the Ottomans and the sharif to a greater extent than did Arabism or Turkism.