Understanding early Islamic history requires knowledge of Central Asia. This site defines Central Asia in a very broad way, to refer to the area east of Iran and west of China. This region joined the Turkic peoples to the north, Iran in the west, and India to the southeast. It was the military heart of the early ʿAbbasid period and a frontier. Under the early ʿAbbasids, the region of Khorasan was ruled by the Tahirids, a family that was loyal to the Caliphate. In the ninth century, though, several emirates emerged in Central Asia. Some acknowledged the ʿAbbasids, even if nominally. The emirs of Central Asia express their own authority in ways that link them conceptually to both Iran and to India.