the few official cross-border trading posts between the two empires, along with Nisibis and Artaxata. The town was near the site of a battle in 531 between Romans and Sasanians, when the latter tried to invade the Roman territories, surprisingly via arid regions in Syria, to turn the tide of the Iberian War. The Persians won the battle, but the casualties on both sides were high. In 542, the city was destroyed by the Persian Emperor Khusrau I (r. 531–579), who razed its fortifications and deported its population to Persia, but it was subsequently rebuilt by Byzantine Emperor Justinian I (r. 527–565). In 580, during another war with Persia, the future Emperor Maurice scored a victory over the Persians near the city during his retreat from an abortive expedition to capture Ctesiphon. In the last years before it came under Muslim rule, Kallinikos was as important as any other urban center in the region, and based on the physical area that it covered it was only slightly smaller than Damascus. Early Islamic period In the year 639 or 640, the city fell to the Muslim conqueror Iyad ibn Ghanm. Since then, it has been known by the Arabic name al-Raqqah, or "the morass", after its marshy surroundings at the time. At the surrender of the city, the Christian inhabitants concluded a treaty with Ibn Ghanm that is quoted by al-Baladhuri. The treaty allowed them freedom of worship in their existing churches but forbade the construction of new ones. The city retained an active Christian community well into the Middle Ages (Michael the Syrian records 20 Syriac Orthodox (Jacobite) bishops from the 8th to the 12th centuries), and it had at least four monasteries, of which the Saint Zaccheus Monastery remained the most prominent one. The city's Jewish community also survived until at least the 12th century, when the traveller Benjamin of Tudela visited it and attended its synagogue. At least during the Umayyad period, the city was also home to a small Sabian pagan community. Ibn Ghanm's successor as governor of Raqqa and the Jazira, Sa'id ibn Amir ibn Hidhyam, built the city's first mosque. The building was later enlarged to monumental proportions, measuring some , with a square brick minaret added later, possibly in the mid-10th century. The mosque survived until the early 20th century, being described by the German archaeologist Ernst Herzfeld in 1907, but has since vanished.