Religio-political leadership. Known as imamate in English. A major practical issue since Muhammad's death in 632. Abu Bakr (first caliph, r. 632–34) and associates regarded the imamate as the right of Muhammad's Meccan Companions who belonged to the tribe of Quraysh (Sunni view). Muhammad's family regarded the imamate as divinely invested in Ali ibn Abi Talib (r. 656–61), Muhammad's cousin, son-in-law, and closest living male relative (Shii view). The dispute ultimately led to the first civil war among Muslims (657–61). The first four caliphs are considered “rightly guided” by Sunnis in their exercise of the imamate, rendering their actions and legal decisions authoritative for all Muslims. Zaydi Shiis believe that the imamate belonged to any member of Muhammad's family who rose against illegitimate rulers. The Imami or Twelver Shii understanding of the imamate is based on the need for an infallible leader and authoritative teacher to guide humanity to prosperous life. Consequently, disregarding and disobeying a rightfully appointed imam is the equivalent of disobeying Muhammad for Shiis.