Battle of Bab al-Abwab (Derbent)

The Battle of Bab al-Abwab (Gate of Gates, modern Derbent) in 22 AH / 643 CE was the northernmost Muslim military expedition of the Rashidun era, pushing into the Caucasus mountain passes. Umar ibn al-Khattab commissioned Suraqah ibn Amr to lead a campaign through Azerbaijan and into the Caucasus. The Muslims captured the ancient fortress city of Derbent on the Caspian coast, which controlled the narrow pass between the Caucasus mountains and the Caspian Sea — the main invasion route between the steppe and the Middle East. The Khazar Kingdom north of the Caucasus became a long-term adversary of the expanding caliphate, eventually defeating the Muslims in later campaigns. The capture of Derbent marked the furthest Muslim advance into the Eurasian steppe during the Rashidun period.