The Himyarite annexed Sana'a from Hamdan around 100 CE. Hashdi tribesmen rebelled against them and regained Sana'a around 180 AD. Shammar Yahri'sh had not conquered Hadramout, Najran, and Tihama until 275 CE, thus unifying Yemen and consolidating Himyarite rule. The Himyarites rejected polytheism and adhered to a consensual form of monotheism called Rahmanism.