The Assyrian Church is the original Christian church in what was once Parthia; eastern Iraq and Iran. Geographically its influence stretched to China and India in the Middle Ages: a monument found in Xi'an (Hsi-an), the Tang-period capital of China (originally Chang'an), in Chinese and Syriac described the activities of the church in the 7th and 8th century, while half a millennium later a Chinese monk went from Beijing to Paris and Rome to call for an alliance with the Mongols against the Mamelukes. Before the Portuguese arrival in India in 1498, it provided "East Syrian" bishops to the Saint Thomas Christians. Patriarch Timothy I (727–823) wrote of the large Christian community in Tibet.