How did Byzantine and Sasanian rivalry affect the Arabian Peninsula?

The long-standing rivalry between the Byzantine Empire and the Sasanian Empire profoundly shaped the Arabian Peninsula by utilizing Arab tribes as frontier guardians and political proxies.12

To secure their borders, the Byzantines relied on the Ghassanid dynasty, while the Sasanians supported the Lakhmid dynasty of al-Ḥīrah. These vassal states acted as buffers against desert tribes and protected vital trade routes. In the south, the competition extended to Yemen, where local leaders sought Sasanian support to expel the Byzantine-backed Aksumite presence, eventually leading to the establishment of a Sasanian satrapy in the region.324

By the early 7th century, the exhaustion caused by a century of warfare between the two empires left both powers vulnerable. When the Arab conquests began, the Byzantine and Sasanian representatives on the northern borders of Arabia lacked the strength to resist. This power vacuum, combined with the internal instability of the Sasanian state, facilitated the rapid expansion of the early Muslim state, which ultimately replaced both empires as the dominant political force in the region.12