Treaty of Bab al-Abwab

Timeline

1. 833–834Caucasus · CaucasusAfter al-Mu'tasim's accession, he intensified military pressure on the Caucasian frontier, suppressing local revolts and repelling Byzantine reinforcements. The empire built and fortified fortresses along the Caspian gate line, creating the military advantage needed to consolidate gains through a treaty.
2. 835Bab al-Abwab (Derbend) · DerbendIn 835, along the line of the Bab al-Abwab fortress, Abbasid authorities concluded a treaty with Caucasian local rulers. The terms regulated tribute, division of defense duties, and passage order, advancing imperial control over the northern frontier from military conquest to an institutional arrangement.
3. 836–838Caucasus · CaucasusAfter the treaty, the Abbasids maintained garrisons and a fortress system along the northern edge of the Caucasus, while local powers paid tribute and assisted in defense as agreed. The northern frontier stabilized, providing rear security for subsequent Abbasid operations such as the expedition against Amorion.