The pass of Derbent (Middle Iranian name is uncertain) was located on a narrow, three-kilometer strip of land in the North Caucasus between the Caspian Sea and the Caucasus mountains. It was in the Sasanian sphere of influence after the victory over the Parthians and the conquest of Caucasian Albania by Shapur I (r. 240/42–270/72– ). During periods when the Sasanians were distracted by war with the Byzantines or conflicts with the Hephthalites in the east, the northern tribes succeeded in advancing into the Caucasus.[1]