In the early 7th century, the Near East was dominated by an epic conflict between the Byzantines and Sasanians. After reaching the gates of Constantinople, the Sasanians were driven back by the Byzantine emperor, Heraclius. Against this backdrop, the Arabian peninsula was, before the explosive arrival of Islam, peripheral to this clash of civilizations. Nomadic tribes inhabited its desert interior, but the coastlines hosted an eclectic jumble of kingdoms: Nestorian Christians in Mazun; a Judaic dynasty in Himyar (until conquest by Axum in 525 CE); the mercantile Quraysh people in Hejaz, who prospered at the crossroads of trade routes between the Mediterranean, Africa and Persia. To the north, the great powers of the region exerted their sway. The Ghassanids were, customarily, a vassal state of the Byzantines, while Lakhm (like the Azd and Kinda, originally one of seven tribes who migrated from Yemen) owed fealty to Sasanian Persia.