MUHAMMAD AL-MAHDI, THE TWELFTH IMAM
Abul-Qasim Muhammad ibn Hasan, known as al-Mahdi (the guided), al-Muntazar (the awaited), al-Hujja (the proof), al-Qaim (the one who will arise). Baqiyatullah (the remnant of God), is identified as the Twelfth Imam. After the death of Hasan al-Askari there was a great deal of confusion among the Shia, with some saying that al-Askari had no son and others asserting that he had. Those who were to go on to become the main body of the Twelver Shia believed that Hasans son Muhammad had gone into occultation.
Bibliography:
See M. Momen, An Introduction to Shii Islam (1985).