From AD second century, the dynamics of the region began to change due to demographic, cultural & geopolitical shifts. Initially, the region witnessed the arrival of large Jewish trader & refugee community from the west. Meanwhile, waves of Arabs(Arabia) from the area around the modern Riyadh began to encroach into neighboring territories. One branch is pushed into Yemen & Oman. The records suggest growing Arab assertiveness against the local clans as their number grew.
Arabia First signs of Proselytization
Around this time, the Byzantines (The eastern Roman Empire with its capital in Constantinople, modern Istanbul) become enthusiastic and proselytizing Christians, & geopolitics took on a religious color. The Byzantine emperor Constantius (337-361) dispatched ambassadors & the missionary Theophilus the Indian to the Himyarite court demanding permission to build churches & proselytize.