Muslim conquest of Azerbaijan

In 643 or years of 22 Hijr, After the conquest of Rayy and Central Persia, Umar ordered the conquest of Azarbaijan. so Rashidun Caliphate continued the conquest towards Azerbaijan first under the force of Al Mughirah bin Shubah. this was also reported by Abu Jafar(Tabari) which quoting the report from Ahmad bin Thabit al Razi.

Battles
later at some points Umar appointed Hudheifa to the command of the campaign against Azarbaijan. Hudheifa first marched to Zanjan. Here the local garrison put up resistance but they were overpowered and the city was conquered. From Zanjan the Muslim forces proceeded to Ardabeel where The Persians in here did not offer any resistance and surrendered on the usual terms of Jizya. From Ardabeel the Muslim forces marched northward along the western coast of the Caspian Sea. There was a confrontation at Bab area which was an important port on the Caspian Sea. this time the Muslims also scored a victory but for unknown circumstances At this stage Hudheifa was recalled. The Persians launched a counter attack causing Muslims abandoned their forward posts in Azarbaijan, as a response Umar now sent the expeditionary forces to Azarbaijan, one led by Bukair ibn Abdullah and the other by Utba bin Farqad. The contingent under Bukair had their first confrontation with the Persians at Jurmizan. The Persians were commanded by Isandiar. In the battle which was quite severe, the Persians were defeated and their commander Isandiar was captured alive. Isandiar asked Bukair, "Do you prefer war or peace." Bukair said that the Muslims preferred peace. Isandiar thereupon said, "Then keep me with you till I can help you in negotiating peace with the people of Azarbaijan". There were many forts in the hills. The Persians went to these hills and shut themselves in the forts. The Muslims captured the entire area in the plains

there's interesting event during the years of 25 Hijr in Islamic Calendar, where the Mushaf Uthmani of Quran was created in attempt to avoid linguistic confusion of Qur'an which translated to local dialect of Azerbaijan and Armenia. Hudhaifa warn Uthman that the new translated Qur'an would lost its original Tafseer if it didnt standardized in original Mushaf or version first before the local could translate and give commentary of Quran interpretation

Aftermath
Bukair ibn Abdullah, who had recently subdued Azerbaijan, was assigned a mission to capture Tiflis. From Bab at the western coast of the Caspian Sea, Bukair continued his march north. Umar decided to practice his traditional and successful strategy of multi-pronged attacks. While Bukair was still miles away from Tiflis, Umar instructed him to divide his army into three corps. Umar appointed Habib ibn Muslaima to capture Tiflis, Abdulrehman to march north against the mountains and Hudheifa to march against the southern mountains. Habib captured Tiflis and the region up to the eastern coast of the Black Sea. Abdulrehman marched north to the Caucasus Mountains and subdued the tribes. Hudheifa marched south-west to the mountainous region and subdued the local tribes. The advance into Armenia came to an end with the death of Caliph Umar in November 644. By then almost the whole of the South Caucasus was captured.

further to 645 forces under Walid Bin Uqba campaigning in four year rotation in two frontier district(Thughur) of Ray and Azerbaijan. one quarter of 40.000 army from Kufa campaigned each year with around 4000 in Ray and 6000 in Azerbaijan