The major constituent tribes or tribal groupings of the Qays were the Ghatafan, Hawazin, Amir, Thaqif, Sulaym, Ghani, Bahila and Muharib.
Many of these tribes or their clans migrated from the Arabian Peninsula and established themselves in Jund Qinnasrin, the military district of the northern region of Syria and Upper Mesopotamia, which long became their abode.
The power of the Qays as a unified group diminished with the rise of the Abbasid Caliphate, which did not derive its military strength solely from the Arab tribes.
Nonetheless, individual Qaysi tribes remained a potent force and some migrated to North Africa and al-Andalus, where they carved out their power.
[1] Unlike most tribes of Arabia, the sources seldom use the term Banū (literally "sons of") when referring to the descendants of Qays.
[3] By the dawn of Islam in the mid-7th century, the descendants of Qays were so numerous and so significant a group that the term Qaysī came to refer all North Arabians.
[10] Qaysi tribes spread throughout Syria and Mesopotamia, particularly in the northern parts of those regions, in the provinces of Qinnasrin (around Aleppo) and Diyar Mudar.
[11] However, they also had a presence around Homs, Damascus, the Ghouta and Hawran plains, the Golan Heights, Palestine, Transjordan (al-Balqa), and in the cities of Kufa and Basra.
[12] Historian W. Mongtomery Watt holds that in the history of Ayyam al-Arab, only individual Qaysi tribes were named, rather than the larger confederation.
[14] The most active Qaysi tribe fighting against the Muslims was the Ghatafan, which attempted several times to capture Mecca before joining the anti-Islamic leader, Tulayha of the Banu Asad.
[14] The pagan Arab tribes were finally defeated in the Battle of Buzakha, after which they once again returned to Islam and submitted to the Muslim state based in Medina.
[14] After the Ridda Wars, Qaysi tribesmen played an important part in the Muslim conquests of Persia under al-Muthanna al-Shaybani and the Levant.
[14] When Yazid and his successor Mu'awiya II died in relatively quick succession in 683 and 684, respectively, the Qays refused to recognize Umayyad authority.
The Kalb and their Yamani allies essentially selected Marwan I to succeed Mu'awiya II, while the Qays largely joined the rebel cause of Abd Allah ibn al-Zubayr.
[14] Fighting in the latter's name, the Qaysi tribes of Amir, Sulaym and Ghatafan under al-Dahhak ibn Qays al-Fihri fought Marwan I and the Yamani faction at the Battle of Marj Rahit in 684.
[16] The Qays were not able to recover from the huge losses they suffered during the late Umayyad period, and their political role, though present, was not of significant consequence during the ensuing Abbasid era.