The Lakhmids were a Southern Arabian tribe of Christians who emigrated in the 3rd Century AD to Southern Iraq founding the ancient city of Al-Hira, which was centered 3 km from modern day Kufa. The Lakhmids were mercilessly conquered by the Sassanid Empire in 330, hereafter retained as feudal proxies in a manner similar to the Ghassanids on the Roman frontier. Lakhmid Christianity differed from the Ghassanid form in that the Lakhmids had accepted the Nestorian argument in Christology, the dual nature of Christ. The Zoroastrian Persians allowed the Lakhmids freedom to practice Christianity, however in political matters they were much less free than their Ghassanid counterparts. After their defeat at the Battle of Hira in 633, at the hands of the Arab armies of Abu Bakr, they became subsumed into the Umma.