Irfan Shahid suspects this part of the tribe either migrated back to Iraq around that time or had remained there, not accompanying their king Imru al-Qays and the rest of the Lakhm to Syria (see below).
Lakhmid history in the 6th century was marked by the long reign of king al-Mundhir III (r. 503–554), who helped extend and protect Sasanian influence in southern and western Arabia, and the war with the Byzantines' Arab vassals, the Ghassanids of Syria.
[5] During the Muslim conquest of Syria, Lakhm tribesmen were counted in the ranks of the Arab tribal fighters led by the Ghassanid chief Jabala ibn al-Ayham in the Byzantine army at the Battle of Yarmouk in 636.
[9] The unclear allegiance of the Lakhm and Judham during the conquest is reflected in Caliph Umar's order to exclude them from shares in the war spoils around 638, which otherwise were to be equally divided among the Arab tribes in the Muslim ranks.
The same had occurred during the battle of Yarmouk and again when the two fought on behalf of Mu'awiya's son, the Umayyad caliph Yazid I, in the Syrian army which suppressed anti-Umayyad rebellions in the Hejaz (Medina and Mecca) in 682–683.
[4] Along with the Judham, and the tribes of Kinana, Azd Sarat, Khuza'a, and Khath'am which arrived with the conquest armies, the Lakhm formed the Arab tribal soldiery of Jund Filastin (military district of Palestine) during the early Islamic period, according to the 9th-century historian Khalifa ibn Khayyat.
[13] While the Lakhm of Syria and Palestine was almost invariably tied with the Judham, their nisba (epithet) continued to evoke honor due to "its archaic flavour, the glorious memories which it recalled" of the kings of al-Hira, according to Lammens.
[4] As late as the 9th and 10th centuries, notable figures in Palestine continued to claim descent from the tribe, such as the scholar Sulayman ibn Ahmad al-Tabarani of Tiberias[14] and messianic anti-Abbasid rebel al-Mubarqa.