The early Muslim conquests, or the early Islamic conquests, also known as the Arab conquests, were a series of wars initiated by the Islamic prophet Muhammad, and continued by the early Muslims. In 622, he established the first Islamic state in Medina, with Muslim armies expanding rapidly out of Arabia under the succeeding Rashidun Caliphate and then the Umayyad Caliphate, culminating in Muslim rule being established throughout most of the Middle East and North Africa, parts of South Asia and Central Asia, and parts of Southern Europe over the following century. According to the Scottish historian James Buchan: "In speed and extent, the first Arab conquests were matched only by those of Alexander the Great, and they were more lasting." At the height of the expansion, Muslim-ruled territory under the Caliphates is estimated to have covered 13,000,000 square kilometres (5,000,000 sq mi), stretching from the Indian subcontinent in the east to the Iberian Peninsula in the west.