The Arabian War of Unification (Arabic: حرب عربية التوحيد) was a conflict in the Middle East, starting with Medinan aggression from Hejaz into Najd and the Trucial Coast states. It ended in the unification of the independent Arabic states into a single nation, the Empire of Mecca.
The War of the Hijaz ended with the success of the Medinan Christian army, led by Fatimah I bin Muhammad, and the unification of the Hijaz tribes with a single official religion, Christianity. The new Medinan state was heavily militant in regards to its faith and wished to spread it amongst the Arabian pagans, and with Saba (now partially Christian and thus possibly easier to convert) already under heavy Ethiopian influence, Fatimah had no option but to look east into the deserts of Najd and the Trucial and Omani coast. After barely a month of preparation and reformation, and before the War of the Hijaz was entirely over, Fatimah sent an ultimatum to all large tribes and holdouts of power in Arabia; bend the knee to a more centralised state or be conquered. While several tribes eventually did give up, most did not, and Fatimah sent her troops into the Nejd.
It seemed that both sides' troops were evenly matched; what Medina lacked in stability (it had just come out of a war) it compensated with a unifying cause; what the pagan Arabians lacked in good armies, they compensated with the huge mobility of their courts. However, the Arabians did not expect such a large rehaul as the Medinan armies, and soon the deadly combination of nomad cavalry's huge mobility and large amounts of discipline took their toll. Within 630 alone, the war was taken halfway across Arabia with most petty kings and tribal lords in the area surrendering. By 631, the King of Kinda surrendered and converted to Medinan Christianity. The war in Nejd was sealed when the Banu Tayy and Banu Kilab surrendered to Medina.
Fatimah continued her attack on the remaining pagans of Arabia centered across the Persian Gulf and Indian Sea coasts. The war here was far quicker and less expensive due to the more sedentary attitude of these tribes. The war ended with the fall of the Banu 'Oman tribes in 632.
The Empire of Mecca annexed the remains of Arabia, except for Saba and westernmost Hadramwt. It became the first proper Arabian centralised state to rule the majority of the nation and soon afterwards propelled itself, due to its stragetic position between the Persian Gulf and the Red Sea and between Persia and Byzantium.