structural:summarization, structural:scholar_edition
Timeline

The Idrisids (Arabic: الأدارسة) were Arab Zaydī Shias whose dynasty, named after its first sultan, Idris I, ruled in the western Maghreb from 788 to 985 CE. Another Zaydī State was established in the region of Gilan, Deylaman, and Tabaristan (northern Iran) in 864 CE by the Alavids; it lasted until the death of its leader at the hand of the Samanids in 928 CE. Roughly forty years later, the Zaydī State was revived in Gilan and survived under Hasanid leaders until 1126 CE. Afterwards, from the 12th to 13th centuries, the Zaydī Shias of Deylaman, Gilan, and Tabaristan then acknowledged the Zaydī Imams of Yemen or rival Zaydī Imams within Iran.

The Buyids were initially Zaydī Shias, as were the Banu Ukhaidhir rulers of al-Yamama in the 9th and 10th centuries. The leader of the Zaydī community took the title of caliph; thus, the ruler of Yemen was known by this title. Al-Hadi Yahya bin al-Hussain bin al-Qasim ar-Rassi, a descendant of Ḥasan ibn ʿAlī, founded the Zaydī Imamate at Sa'dah in 893–897 CE, and the Rassid dynasty continued to rule over Yemen until the middle of the 20th century, when the republican revolution of 1962 deposed the last Zaydī Imam. (See: Arab Cold War). The founding Zaydī branch in Yemen was the Jarudiyya; however, with increasing interaction with the Ḥanafī and Shāfiʿī schools of Sunnī jurisprudence, there was a shift from the Jarudiyya group to the Sulaimaniyya, Tabiriyya, Butriyya, and Salihiyya. Zaydī Shias form the second dominant religious group in Yemen. Currently, they constitute about 40–45% of the population in Yemen; Jaʿfaris and Ismāʿīlīs constitute the 2–5%. In Saudi Arabia, it is estimated that there are over 1 million Zaydī Shias, primarily based in the western provinces.

Currently, the most prominent Zaydī political movement is the Houthi movement in Yemen, known by the name of Shabab al-Mu'mineen ("Believing Youth") or Ansar Allah ("Partisans of God"). In 2014–2015, Houthis took over the Yemeni government in Sana'a, which led to the fall of the Saudi Arabian-backed government of Abd Rabbuh Mansur Hadi. Houthis and their allies gained control of a significant part of Yemen's territory, and resisted the Saudi Arabian-led intervention in Yemen seeking to restore Hadi in power. (See: Iran–Saudi Arabia proxy conflict). Both the Houthis and the Saudi Arabian-led coalition were being attacked by the Sunnī Islamist militant group and Salafi-jihadist terrorist organization ISIL/ISIS/IS/Daesh.