Zaydiyyah is a Shi"ite school of law which, of all the groups in Shi"a, is closest to the Sunni tradition. The Zaydis are principally distinguished from other Shi"ite groups in their conception of the nature of the Imamate. Unlike the Imamis and Isma"ilis, who believe that the Imamate is handed down through a particular line of descendants, the Zaydis believe that anyone in the house of Ali is eligible for the Imamate. The Zaydis reject the doctrine of the Hidden Imam and the return of the Mahdi. The Imam is regarded as neither infallible nor capable of performing miracles. Personal merit, rather than investiture, governs who should be made Imam.
The Zaydis reject any form of "sufi" tradition. Theologically they are closest to the Mu"tazila school.
The term "Zaydi" is applied to the followers of Zayd b. Ali, the grandson of al-Husein (the son of the fourth caliph, Ali) and half-brother of the fifth Imam, Muhammad al-Baqir. Zaid b. Ali was killed in 740 in an uprising against the Ummayad Caliph al-Hisham.
In the 9th century two Zaydi states were established: one in Tabaristan, a region south of theCaspian Sea, and the other inYemen. The Zaydi state came to an end in 928 when its ruler, al-Hasan ibn al-Qasim, fell in battle. However, in 964 a second Zaydi Imamate was established; this lasted until the twelfth century. From the twelfth century the Zaydi communities declined in importance and during the fifteenth and sixteenth centuries were gradually incorporated into the Twelver Shi"a. The Yemeni state of Zaydis was founded in 890 by Yahya ibn al-Husseinn and has lasted up until the present day. In spite of internal fighting over succession and attacks from the Isma"ilis, the Yemeni state retained its independence until 1539 when it was conquered by the Ottoman Turks and became a province within the Ottoman empire. In 1595 the Yemen Zaydis declared war on the Turks, which finally led to the departure of the last Ottoman governor in 1635. The Yemen retained its
independence until 1872 when once again it became a province within the Ottoman Empire. De facto independence was achieved during the First World War and actual independence with the fall of theOttoman Empire after the First World War.
Following the dissolution of the Ottoman Empire Imam Yahya was left in control of theYemen. In 1948 Imam Yahya was assassinated in an attempted palace coup. The coup was defeated by Yahya"s son, Ahmad, who succeeded his father as Imam. When Imam Ahmad died in September 1962 he was succeeded by his son,
Muhammad. A week later an army coup deposed the Imam established the Yemen Arab Republic. Since that time the Imamate has remained vacant.
Zadiyyah does not have a distinctive symbol system.
Zaydis are estimated to constitute 8 million of the some 70 million Shi"ite population of the world (Yann Richard, Shi"ite Islam (Oxford University Press, 1995).
Zaydiyyah has no headquarters or such. It is, however, the official school of the Yemen.