Ideology calling for sociopolitical solidarity among all Muslims. Has existed as a religious concept since the early days of Islam. Emerged as a modern political ideology in the 1860s and 1870s at the height of European colonialism, when Turkish intellectuals began discussing and writing about it as a way to save the Ottoman Empire from fragmentation. Became the favored state policy during the reign of Sultan Abdulhamid II (r. 1876 – 1909 ) and was adopted and promoted by members of the ruling bureaucratic and intellectual elites of the empire. With the rise of colonialism, became a defensive ideology, directed against European political, military, economic, and missionary penetration. Posed the sultan as a universal caliph to whom Muslims everywhere owed allegiance and obedience. Sought to offset military and economic weakness in the Muslim world by favoring central government over the periphery and Muslims over non-Muslims in education, office, and economic opportunities. Ultimately failed and collapsed after the defeat and dismemberment of the Ottoman Empire after World War I. Resurrected during the resurgence of Islam after World War II. Expressed via organizations such as the Muslim World League and the Organization of the Islamic Conference, which seek to coordinate Islamic solidarity through political and economic cooperation internationally. Has also served as an important political tool in recruiting all-Muslim support against foreign aggressions.