Salman the Persian
With the help of the exiled Banu Nadir, the Quraysh military leader Abu Sufyan mustered a force of 10,000 men. Muhammad prepared a force of about 3,000 men and adopted a form of defense unknown in Arabia at that time; the Muslims dug a trench wherever Medina lay open to cavalry attack. The idea is credited to a Persian convert to Islam, Salman the Persian. The siege of Medina began on 31 March 627 and lasted two weeks. Abu Sufyan's troops were unprepared for the fortifications, and after an ineffectual siege, the coalition decided to return home. The Quran discusses this battle in sura Al-Ahzab, in verses .