As Bill Kochman explains in the series "2012: New Age Deception And Psychobabble
", the term "Mahdi" is associated with both the Shi'a and Sunni branches of Islam, and refers to the long-anticipated Muslim messiah.
According to Islamic belief, there have been twelve divinely anointed leaders of Islam, since the religion was founded by Muhammad during the early 7th century. The final leader, Muhammad al-Mahdi, is said to have disappeared, and is believed by most Muslims to currently be in occultation, or hidden from public view.
However, certain hadith prophesy that Muhammad al-Mahdi will one day soon return as a great leader and messiah. Some of the hadith state that the Mahdi -- his name means "the Guided One" -- will with Jesus working by his side, destroy "Masih al-Dajjal", who in English is known as "the False Messiah", "the Deceiving Messiah", "the False Prophet" or "the Great Deceiver". Some Muslims believe that al-Dajjal will appear somewhere between Syria and Iraq, and that he will create an army from the people whom he has deceived. al-Dajjal will then wage war against Jesus, who will be leading the Army of the Righteous. However, Muslims also believe that Jesus -- under the leadership of the Mahdi -- will then say that everyone must submit to Islam, or else be destroyed.
Please also refer to the terms "Twelver
" and "Masih al-Dajjal
" for additional information, as well as the article To Tell The Truth : Moshiach, Mahdi Or The Messiah?