Battle of Qadisiyya in the context of "Rashidun army"

The Lakhmid kingdom (Arabic: اللخميون al-Lakhmiyyūn), also referred to as al-Manādhirah (المناذرة) or as Banū Lakhm (بنو لخم), was an Arab kingdom that was founded and ruled by the Lakhmid dynasty from c. 268 to 602. Spanning Eastern Arabia and Southern Mesopotamia, it existed as a dependency of the Sasanian Empire, though the Lakhmids held al-Hira as their own capital city and governed from there independently. The kingdom was a participant in the Roman–Persian Wars, in which it fought as a Persian ally against the Ghassanid kingdom, which was ruled by a rival Arab tribe and existed as a dependency of the Roman Empire. While the term "Lakhmids" has been applied to this kingdom's ruling dynasty, more recent scholarship prefers to refer to them as the Naṣrids.

The Nasrid dynasty's authority extended over to their Arab allies in Al-Bahrain (eastern cost of Arabia) and Al-Yamama. In 602, the Persian king Khosrow II deposed and executed the last Nasrid ruler Al-Nu'man III and annexed the Lakhmid kingdom, triggering a revolt by his Arab allies in Najd. The ensuing disorder between anti-Persian rebels and pro-Persian loyalists in the kingdom culminated in the Battle of Dhi Qar, which resulted in a defeat for the Persian army and their loyalists, thereby ending the Persian hegemony over Eastern Arabia. The success of the rebellion and the victory against the Persians at Dhi Qar roused political confidence, enthusiasm, and self-consciousness among the Arabs. Coupled with increasing instability in Persia proper after the downfall of Khosrow in 628, these events heralded the decisive Battle of Qadisiyya in 636 and the Muslim conquest of Persia.