BĀB AL-ABWĀB ("Gate of the Gates"; Persian Darband ; modern *Derbent ), a pass and town at the eastern end of the Caucasus range, where the road narrows between the mountains and the Caspian Sea. Bāb al-Abwāb is mentioned in both the "Letter of Ḥasdai" and the "Reply of King Joseph" (see *Khazars), in the latter specifically as marking the southern limit of the Khazar domain. This agrees in general with the accounts of the Arabic geographers and historians. The latter described Bāb al-Abwāb as guarding one of the two main passes of the Caucasus through which the Khazars invaded the lands of Islam. Extensive arrangements for the defense of Bāb al-Abwāb are reported by the geographer al-Iṣṭakhrī (tenth century). Previously, the town had more than once been overrun from the north, though the successful Khazar attack against Ardabil (apparently in 730), referred to in the "Reply of King Joseph," was made via Dariel (now Daryal).
Dunlop, Khazars, index; Dunlop, in: eis2 (incl. bibl.); al-Iṣṭakhrī, Kitāb al-Masālik wa-al-Mamālik (1961), 109–10; M. Artamonov, Istoriya Khazar (1962), index.
[Douglas Morton Dunlop]