The conquest of Iranian Azerbaijan started in 651, part of a simultaneous attack launched against Kerman and Makran in the southeast, against Sistan in the northeast and against Azerbaijan in the northwest. Hudheifa marched from Rey in central Persia to Zanjan, a well-fortified Persian stronghold in the north. The Persians came out of the city and gave battle, but Hudheifa defeated them, captured the city, and those who sought peace were granted it on the usual jizya conditions.

Hudheifa then continued his march north along the western coast of the Caspian Sea and captured Bab al-Abwab by force. At this point Hudheifa was recalled by Uthman, to be replaced by Bukair ibn Abdullah and Utba ibn Farqad. They were sent to carry out a two-pronged attack against Azerbaijan: Bukair along the western coast of the Caspian Sea, and Uthba into the heart of Azerbaijan.

On his way north Bukair was halted by a large Persian force under Isfandiyar, the son of Farrukhzad. A pitched battle was fought, after which Isfandiyar was defeated and captured. In return for his life, he agreed to surrender his estates in Azerbaijan and persuade others to submit to Muslim rule. Uthba ibn Farqad then defeated Bahram, brother of Isfandiyar. He too sued for peace. Azerbaijan then surrendered to Caliph Umar, agreeing to pay the annual jizya.