Name the span of years that saw the greatest expansion of the muslim empire (justify your answer)

The Muslim Empire comprised the timespan in which three different Caliphates ruled:

The Rashidun Caliphate (632–661) which supposed the start of the Muslim Empire, established after the death of the Profet Muhammad. It was a period characterized by a quick military expansion, which took control over the following territories: the Arabian Peninsula including the Levant, the Transcaucasus region in the North, the Northern Africa area from Egypt to the current territory of Tunisia as the Western border and, finally, the Iranian plateau including parts of Central Asia and South Asia as the Eastern limit. The Umayyad Caliphate (661–750). More conquest were achieved, and to the formerly mentioned ones, the following territories were annexed: the Transoxiana, Sindh, the Maghreb and the Iberian Peninsula (named Al-Andalus).The Abbasid Caliphate (750–1258), was the third caliphate and established its central government in Kufa, located in current Iraq. In 762 the caliph Al-Mansur founded the city of Baghdad. The caliphate started to lost authority in the Western regions (Al-Andalus and Maghreb for example) but also reinforced control over territories on the East, for instance, the Mesopotamian domain.