Twelver Shia Islam had, since the ninth century, held that its Twelfth Imam did not die but went into occultation, and that during a period called the Minor Occultation he communicated with the faithful through a series of deputies, each called a Bab, a Gate. When Siyyid Ali Muhammad, a young merchant from Shiraz, first announced his mission to Mulla Husayn on the night of 22 May 1844, the title he took, the Bab, placed him inside that established expectation rather than outside it: a channel to the hidden Imam, not a replacement for the Islamic revelation itself.
Over the six years between that declaration and his execution in 1850, his own writings pressed the claim further, moving from gate to imam, to imam himself, and eventually to an independent Manifestation of God comparable in kind to Muhammad, bearing his own revealed book, the Bayan, and his own law. Each stage of the escalation is documented in his surviving writings and correspondence, which is part of why Denis MacEoin's manuscript-based reconstruction of Babi history treats the movement's theology as something that developed in real time under the pressure of persecution, rather than as a fixed system announced complete on day one.